If cost is an issue, just buy the least expensive folding tire you can buy with kevlar lining. There are lots of good options. I've been commuting on Continental GP 4000s that I bought when they were on sale for $25. They now cost more than $40, so if I was shopping for new tires I might buy something else that was less expensive -- like Vittoria Rubinos, Michelin Krylions, Conti Gatorskins.

Check www.probikekit.com. The generally have some good tires on sale for very good prices, with free shipping from England.