I have yet to find a good picture of a pardessus on the net. However there are several bizarre instruments in Vienna. Most viol makers build one or several models of pardessus. Original instruments are frequently being sold either by members of the Viola da Gamba Society of America the Viola da Gamba Society of Great Britain and the Societe Francaise de Viole . I play a five string pardessus after Guersan made by Marco Turnovec, Iddergem, Belgium.
Strings are a tricky thing for pardessus.
It take a great amount of experimentation to find the right combination for your instrument. I have tried strings by Kirschner, Pirastro and Boston Catline. There are also strings available from Damian Dlugolecki and Aquila . You can however substitute other instruments strings for the pardessus rather easily. There are only three recordings of the pardessus that I am aware of.