for quick or cheap:

-ebay
-autozone has some decent ones for intake pipe, i used a few in a bind, but i dont know how well they handle pressure pipes.

i get all of mine from ATP Turbo. they are 3-ply, usually pretty good for most setups. There are 5 ply ones from Forge Motorsports in Orlando that are really baller. Expect to pay for the good ones, no ways around that.