<PAGE>   1
                                                                   Exhibit 10.39


                          VENDOR LEASE PLAN AGREEMENT

         THIS VENDOR LEASE PLAN AGREEMENT (the "Agreement") is effective as of
the date of execution, by and between FIRST SIERRA FINANCIAL, INC. ("First
Sierra") and MANSUR INDUSTRIES INC. ("Mansur") and cancels and supersedes the
Vendor Lease Plan Agreement between Oakmont Financial Services, now a
subsidiary of First Sierra, and Mansur dated the 28th day of May, 1996 (Exhibit
1).

     1.   LEASE PROGRAM. First Sierra offers leasing and financing programs to
          assist manufacturers, distributors and dealers in facilitating the
          acquisition of equipment by their customers. Mansur wishes to have
          First Sierra provide a leasing and financing program for Mansur's
          customers. First Sierra and Mansur have agreed that First Sierra will
          offer this program under the terms described in this Agreement.

     2.   ACCEPTANCE BY FIRST SIERRA. First Sierra shall purchase transactions
          upon execution of an assignment by Mansur on the First Sierra
          assignment form (Exhibit 2) and pursuant to the First Sierra credit
          guidelines and pricing schedule (Exhibit 3). First Sierra is not
          obligated to accept any transaction submitted to First Sierra by
          Mansur unless the transaction in First Sierra's reasonable judgement
          complies with First Sierra's then applicable credit criteria. Mansur
          may request a credit or documentation exception by following the
          procedure described herein. Mansur may, at its option, submit any
          transaction declined by First Sierra or any transaction not meeting
          the First Sierra credit guidelines to any third party leasing company
          of its choice. If First Sierra declines over fifteen (15%) percent of
          the leases submitted over any thirty (30) day period that are in
          accordance with the First Sierra credit guidelines herein, which
          leases are financed by a third party leasing company on substantially
          the same terms and conditions declined by First Sierra, Mansur may,
          at its sole option, upon thirty (30) days written notice to First
          Sierra, terminate this Agreement without penalty. In such event,
          transactions approved but not yet funded by First Sierra shall be
          funded pursuant to this Agreement.

     3.   MANSUR WARRANTIES. In addition to any warranties Mansur may make
          pursuant to First Sierra's purchase of equipment, Mansur makes the
          following further representations and warranties related to each
          lease, each such warranty and representation to speak as of the
          funding by First Sierra respecting the transaction:

          (a)  To the best of Mansur's knowledge, the lessee will use the
               equipment for commercial purposes;

          (b)  The lease and each other instrument, including but not limited
               to guaranties, executed in connection therewith and all
               signatures thereon are genuine; the lease has been duly
               authorized and executed by the named lessee and/or an authorized
               representative thereof; the lease correctly sets forth the
               initial payment due upon delivery and acceptance of the
               equipment and the rentals or installment payments to which the
               lessee is obligated for the term of the lease; the equipment is
               fully and correctly described in the lease and has been
               delivered to the lessee at the location(s) indicated on the
               lease; and the equipment has been accepted by the lessee for all
               purposes of the lease.


<PAGE>   2


          (c)  There are no representations and warranties not set forth in the
               lease that have been made by Mansur to the lessee with respect
               to the lease of the equipment other than those of which First
               Sierra is aware, and, without limiting the foregoing, Mansur has
               not made any representation not set forth in the lease that the
               lease is terminable by the lessee if the lessee is unsatisfied
               with the equipment for any reason or that the lessee may
               trade-in the equipment;

          (d)  All dealings by Mansur with the lessee, including in connection
               with any advertisements or purchase orders relative to the
               lease, and the execution of the lease if procured by Mansur have
               been in accordance with all applicable laws and regulations;

          (e)  The conduct of Mansur in developing the lease transaction shall
               not subject First Sierra to liability under any suit or
               administrative proceeding under any state or federal law, rule
               or regulation, it being understood, without limiting the
               generality of the foregoing, that the lease transaction shall be
               assumed to constitute "credit" as that term is defined and used
               in the Equal Credit Opportunity Art (or applicable State Law),
               implementing regulations and official interpretations of the
               Federal Reserve Board Staff.

          (f)  The lessee has and shall have no defense, offset or counterclaim
               as to the enforcement of the lease arising out of the conduct of
               Mansur, and without limiting the generality of the foregoing,
               Mansur is not in default in any of Mansur's obligations to the
               lessee;

          (g)  Mansur does not know of any fact that indicates the
               uncollectibility of the lease;

          (h)  The lessee's application correctly sets forth all information
               given Mansur by the lessee. Mansur has provided First Sierra any
               other credit information Mansur has with respect to the leases
               and all such information is true and correct to the best of
               Mansur's knowledge;

          (i)  Except monies which First Sierra has agreed are to be retained
               by Mansur, Mansur has not received any monies from the lessee
               related to the equipment which Mansur has not transferred to
               First Sierra, properly endorsed to First Sierra where
               appropriate, or which were loaned by Mansur to the lessee;

          (j)  If the transaction is an equipment lease, title to the equipment
               has vested in First Sierra free and clear of any liens of
               persons claiming by, through or under Mansur, and if the
               transaction is a financing, such title has vested in the lessee.

     4.   MANSUR'S CONTINUING OBLIGATIONS. Mansur shall:

          (a)  at the request of First Sierra or the lessee, provide at
               commercially reasonable prices full, complete and adequate
               service, including warranty service, for the relevant equipment
               in conformity with standard trade practices;

          (b)  takes such action as is reasonably necessary or as First Sierra
               may reasonably request to evidence and perfect this Agreement
               and First Sierra's rights contemplated hereby;


                                       2
<PAGE>   3


          (c)  turn over promptly to First Sierra in the form received,
               properly endorsed to First Sierra where appropriate, any monies
               received by Mansur relative to a lease following its funding by
               First Sierra, unless the lease has been purchased by Mansur
               under paragraph 10;

          (d)  not represent that it is the agent of First Sierra nor make any
               reference to First Sierra in any advertising materials of Mansur
               without First Sierra's prior written consent;

          (e)  not repossess any equipment or accept redelivery of any
               equipment from a lessee without the prior consent of First
               Sierra; and

          (f)  if any equipment is repossessed by (or surrendered to) First
               Sierra or pursuant to First Sierra's request prior to all lease
               obligations being fulfilled, upon request of First Sierra,
               utilizing a reasonable and non-discriminatory "first in/first
               out" approach, Mansur shall assist First Sierra in remarketing
               any such equipment from a lessee. If Mansur is successful in
               remarketing such equipment, First Sierra shall pay Mansur a fee
               equal to $150.00 per unit of equipment for services rendered by
               Mansur in remarketing such repossessed or surrendered equipment.

     5.   SALE OF EQUIPMENT AT FMV TO MANSUR UPON EXPIRATION OF LEASE TERM.
          Provided that the lease does not contain a purchase option to the
          lessee and provided all rental and other monies due First Sierra have
          been fully paid, upon the expiration of the customer's original lease
          term First Sierra agrees to provide Mansur with an option to
          repurchase from First Sierra, for a cash purchase price equal to the
          fair market value of the Equipment plus applicable sales tax, all
          Equipment which is the subject of the lease. The fair market value
          shall be an amount mutually agreed upon by First Sierra and Mansur;
          provided that if the parties are unable to agree upon the fair market
          value, such fair market value shall be determined by an appraiser
          selected by mutual agreement. Upon payment by Mansur, First Sierra
          shall assign and release to Mansur any and all interest First Sierra
          may have in the equipment. Delivery of any equipment repurchased by
          Mansur shall be the sole responsibility of Mansur.

     6.   DOCUMENTATION DISCLAIMER. Mansur and First Sierra acknowledge that
          the documents required and provided by First Sierra in connection
          with the documentation of a transaction hereunder have been prepared
          by First Sierra for the purpose of First Sierra's leasing or
          financing activities. Mansur further acknowledges that First Sierra
          makes no warranty of any nature whatsoever, express or implied, with
          respect to the form, substance or enforceability of any such
          documentation. Use by Mansur of any such documentation for its own
          purpose is at Mansur's own risk. If Mansur uses any such
          documentation for such purposes, Mansur shall make certain that no
          reference whatsoever to First Sierra appears thereon.

     7.   NOTICES. Notices hereunder must be in writing addressed to the
          respective party at the appropriate address set forth at the foot
          hereof or such other address of which the party may give the other
          notice and shall be mailed, certified U.S. mail with postage prepaid.
          Notices shall be effective two (2) days after such mailing. Each
          party shall provide the other notice of a change in such party's
          address.


                                       3
<PAGE>   4


     8.   TERMINATION. This Agreement shall be for an initial term of one (1)
          year and shall automatically be renewed for successive one (1) year
          terms; Each party may terminate this Agreement, with or without
          cause, upon sixty (60) days notice to the other party unless
          terminated under paragraph 2 hereof. Termination of this Agreement
          will not affect the rights and obligations of either party as to
          previously consummated or approved leases, including as respects
          paragraph 10; provided that if termination follows a breach by Mansur
          of any of Mansur's warranties or agreements under this Agreement,
          First Sierra may terminate its obligations as to any previously
          approved but unfunded transactions.

     9.   REMEDIES. The purchase of interests in equipment covered by this
          Agreement is non-recourse except as provided herein. If Mansur
          breaches any warranty under this Agreement and First Sierra incurs a
          loss with respect to a specific lease as a result of such breach, and
          such breach is not cured within thirty (30) days of First Sierra's
          notice to Mansur thereof, Mansur shall be granted ninety (90) days
          thereafter to repossess and remarket the equipment under such lease
          on behalf of First Sierra and pay to First Sierra an amount equal to
          ninety (90) days of interest at the then current prime rate on the
          present value of the remaining payments or, in the event Mansur fails
          to successfully remarket such equipment, Mansur shall be obligated to
          repurchase the lease and First Sierra's rights under all related
          agreements and First Sierra's interest in the equipment for an amount
          equal to the present value of the remaining payments at the prime
          rate in effect at the first day of the month immediately preceding
          the assignment of the lease from Mansur to First Sierra less one
          hundred dollars ($100.00), assuming no recovery by First Sierra from
          disposition of the equipment, less any applicable deposit which First
          Sierra will retain plus applicable taxes. Upon receipt of the
          applicable payment, the lease and First Sierra's rights under the
          related documents will be sold to Mansur as is where is, without any
          warranty, except in each case a warranty that title to such equipment
          is being transferred by First Sierra to Mansur. Until First Sierra
          has received the purchase price, Mansur will have no interest in the
          interests to be purchased. If, however, after demand by First Sierra
          but prior to payment Mansur is deemed to have acquired any such
          interest, First Sierra will have a security interest therein under
          the Uniform Commercial Code as a security for the performance by
          Mansur of Mansur's obligations hereunder.

     10.  AMENDMENTS. This Agreement may be amended only by a writing signed by
          both parties. Acceptance of an amendment by the parties shall be
          manifested by and be effective upon the date of the first transmittal
          to First Sierra of an application to consummate a lease or submission
          of a documentation package.

     11.  LEASE CONSUMMATION. Mansur and First Sierra agree that First Sierra
          shall use the credit criteria found on Exhibit 3 to determine the
          creditworthiness of an applicant. With respect to any lease or
          financing (any such lease or financing a "lease") Mansur wishes to
          arrange, Mansur will, before delivery of the related equipment,
          furnish First Sierra with an equipment description, the transaction
          proposed terms, credit information Mansur has received regarding each
          lessee or purchaser in connection with the transaction (individually
          or collectively as the context indicates the "lessee") and such other


                                       4
<PAGE>   5


          information as First Sierra may reasonably request. Upon receipt of
          all requested materials, First Sierra will review the package and
          advise Mansur of its decision within 2 business days of receipt of
          the completed package for all transactions under $150,000 and within
          4 business days of receipt of the completed package for all
          transactions over $150,000. Documentation as to approved leases will
          be prepared by First Sierra and procured by First Sierra and/or
          Mansur as First Sierra reasonably directs utilizing the then current
          rates for this program. Mansur will not, unless otherwise consented
          to by First Sierra, deliver any equipment before receipt of First
          Sierra's approval or rejection advice. When the documents required by
          First Sierra as to a transaction are received by First Sierra, with
          each properly completed within the specified commitment period, First
          Sierra will complete the transaction and fund the advance for the
          transaction within ten (10) business days after the delivery and
          acceptance of the equipment, which will be calculated in the manner
          agreed to by the parties from time to time. In the event a particular
          applicant does not meet the minimum credit criteria, Mansur may
          request First Sierra to make an exception. In such event, an
          exception request form shall be submitted by Mansur to First Sierra
          (see Exhibit B) and shall be considered by First Sierra.

     12.  FIRST SIERRA SUPPORT. In consideration of Mansur's Volume Commitment
          and in order to facilitate and maximize production under this
          Agreement, First Sierra will place one or more employees, as
          required, at Mansur's corporate headquarters in Miami, Florida to act
          as the "program manager" responsible for coordinating applications,
          resolving credit and documentation issues and to maintain the level
          of the program as established herein. The authority of the program
          manager shall be determined by First Sierra in its sole discretion,
          and any deviation from credit or documentation requirements shall be
          approved by an officer of First Sierra. The program manager shall
          have no authority to modify this Agreement. Mansur, at its expense,
          will provide the program manager with physical facilities and support
          sufficient to perform duties effectively. First Sierra shall provide
          additional necessary administrative support, from time to time, as
          required to properly and effectively manage Mansur's growing volume
          of transactions. First Sierra shall ensure that all credit approvals
          and documents are completed within two (2) business days from the day
          the transactions are submitted in accordance with the First Sierra
          credit guidelines, provided all fully and properly completed
          applications (the form of which shall be mutually agreed upon by
          First Sierra and Mansur), guarantees and other instruments required
          in connection with the lease transaction are properly and completely
          submitted to First Sierra by Mansur. In addition to the program
          manager and any required administrative support, First Sierra shall
          agree to provide the professional services of Charles V. Litt to
          assist in the negotiation and management of accounts and for
          marketing support as Mansur may reasonably request. Mansur agrees to
          reimburse First Sierra for all travel related expenses reasonably
          incurred by Charles V. Litt, other than expenses incurred as a result
          of normal and routine lease negotiation and transaction, including by
          way of example but not limited to, participation at trade shows,
          developmental meetings and other special requirements of Mansur as it
          relates to Mr. Litt's services.


                                       5
<PAGE>   6


     13.  VOLUME COMMITMENT. Mansur estimates that for the period of January 1,
          1999 through December 31, 1999 it will submit no less than
          $15,000,000 (based on equipment cost) of proper and complete
          transactions to First Sierra in accordance with First Sierra's credit
          guidelines. If Mansur does not submit this amount, it shall, no later
          than January 31, 2000, pay First Sierra a fee of three (3%) percent
          of the difference between $15,000,000 and the amount below
          $15,000,000 which is actually submitted, but in no event more than
          $150,000. In the event that this Agreement is terminated by Mansur
          prior to December 31, 1999 pursuant to the termination provisions
          contained herein, the minimum volume commitment in the amount of
          $15,000,000 and the maximum fee set forth above in the amount of
          $150,000 shall be prorated on the basis of the number of days the
          Agreement has been in effect during 1999 divided by 365, but subject
          to a minimum fee of $75,000. In the event that this Agreement is
          terminated by Mansur pursuant to the termination provisions of
          paragraph 2 herein or if termination follows a breach by First Sierra
          of any of First Sierra's warranties or agreements under this
          Agreement, Mansur shall not be subject to any volume commitment or
          payment of any fee. Each year thereafter, on or before the one year
          anniversary date of this Agreement, Mansur and First Sierra will
          establish the volume commitment for the following year.

     14.  GENERAL PROVISIONS. This Agreement constitutes the entire agreement
          of the parties as to the leasing and financing program First Sierra
          will make available to Mansur. In the event either party institutes
          legal proceedings to enforce any of the terms of this Agreement, the
          prevailing party in such proceedings will be entitled to recover its
          attorneys' fees and costs incurred therein. It is the intent of the
          parties that this Agreement be enforced to the fullest extent, and
          any provision of this Agreement deemed by a court to be unenforceable
          will be deemed deleted to the extent only of such unenforceability.
          The singular number includes the plural, and the neuter gender the
          masculine or feminine where the context requires. This Agreement
          inures to the benefit of, and is binding upon, the heirs, legatees,
          personal representatives, successors and assigns of the parties, it
          being understood however, that neither Mansur nor First Sierra may
          assign its rights or duties hereunder without the prior written
          consent of the other party. Time is of the Essence of this Agreement.
          The headings to the paragraphs of this Agreement are for convenience
          only and are not to be used in the interpretation of this Agreement.


          FIRST SIERRA FINANCIAL, INC.           MANSUR INDUSTRIES INC.
          600 Travis Street, Suite 705           8305 NW 27th Street, Suite 107
          Houston, TX 77002                      Miami, FL 33122


          By:/s/ Greg McIntosh                   By:/s/ Paul I. Manur
             ---------------------------            ---------------------------

          Its: Executive V.P.                    Its: C.E.O.
             ---------------------------            ---------------------------

          Date: November 15, 1998                Date: November 9, 1998
               -------------------------              -------------------------


                                       6