Tubes for 700C and 27" are often interchangable - though not all brands are labelled that way. Performance's 700x35-38 is labelled as being interchangable with 27x1 1/4 - should be the same across brands. So finding tubes shouldn't be too big a deal, and I'd expect to find tires without too much trouble, too, since there are still TONS of bikes from the 70s and 80s ont he roads that use them. Avoid the Wal-Mart cheapies, though - I grabbed one when I was in a tight spot a while ago, and I had to go through a big stack of them before I found one with a reasonably even bead all the way 'round... lousy quality control!

-chris