Where to get polyethylene, PVC, or Hypalon sheets?

[SWG]

Well, I'm playing around with idea of trying to make an inflatable boat. But to do this I need certain materials which I don’t think I can find at Home Depot.

I know it's godda be out there somewhere because I know people who make green houses usually use the same type of sheet-plastic I think I am looking for as walls/insulation.

Any known-name stores in the US you guys know off the top of your head?

[SCUBAnut]

Check www.mcmastercarr.com