Used Pin Lock Style Kegs from Adventures in Homebrewing.  These are pressure tested and guaranteed to hold pressure.  22-24″ Tall, 9″ Wide.  Heavy Duty Stainless Kegs.  Satisfaction Guaranteed.  A set of new o-rings are also included. 

AIH has generally great availability and great deals on these kegs.  Check product page for current price, description and availability. 

=5 Gallon Cornelius Keg Pin Lock Used (Coke) – via Adventures in Homebrewing

Note that these are also available in four packs

Also: Kegerator Tips & Gear | Keg Repair Part #s | Recent Keg Finds