take a look at the pnuematics control industry. Just make sure you let them know the operating temp and that you want food grade. Most plumbing type suppliers will look at you blankly.
Depending on where you live Festo or SMC resellers or even Hydraulic companies that do air should be a help.
Check out SMC for Flourpolymer tubing 200 C medical rated :) http://www.smcaus.com.au/pages/product_selection.html#