Classic Shaving has some nice towels. That's what I use too.
http://www.classicshaving.com/Grooming_Needs.html
I use those "micro fiber" kitchen towels. Thicker than normal kitchen towels and the right size for your face.
Another good choice for soaking your face for a Kyle's Prep is the traditional chamois cloth that they sell to wash cars with. Be sure to buy a good one, i.e. one that is fairly thick. It holds A LOT of water, it feels really super soft on the skin, and it lasts forever. You just want to use water on this cloth, not soap. Just wring it out really well when you're done, stretch it a little to maintain the original shape, and hang it up to dry.
Classic Shaving has some nice towels. That's what I use too.
http://www.classicshaving.com/Grooming_Needs.html