Look in the yellow pages under - Plastic - Sheet, Rod, Tube, Film or something similar.
I found a company in my area that is called Acme Plastics. They carry a decent stock, but their prices are kind of high. If you live in a larger area, you may find better pricing due to the competition.
Fergy preaches that only domestic cast should be used in our applications. The only domestic products available are Spartech Polycast, Cyro Acrolite GP, and Atofina PlexiGlass-G.
Louey