The site I generally use is Vampfangs.com but unfortunately there prescription section isn't too huge, however if you sign up for there free stuff club every other month or so I get a coupon for 20% of contacts which is pretty nice. There is also Grimmbrothershalloween.com which i've used before too, there custom section has more available for prescription but they're pretty expensive compared to the non prescription ones. For the record though, I have horrible eyes, but my Keely contacts aren't prescription and I find I really don't have that much trouble playing in them.
Good luck!
~Stacey