Try this link.....
Sunray, Inc. Polyurethane Products
I have made a bunch of wheels myself but in all cases the difficulty is making them true. I even found some 8" wheels, poly covered (I think) for $5. Next my focus is going to be on making some from MDF wood (lighter wood). The prior ones I used Corian kitchen countertop material and laminated the layers together. Those are at a machine shop for truing right now. The truing will cost me apprx $20 for each wheel. There re many ways to skin a cat!