Yes, the 165r15 (165/80/15) is getting VERY hard to find! Tire Rack has had them on backorder for quite a while, Jegs lists them but they are not in stock, and most local tire places dont carry them or list that size any longer.
Coker Tire lists them on their site, but I dont know if they have them in stock or not. If you find them, please be sure to let us know where!
I had a hell of a time finding 165 tires for my skinnies when I was getting ready to buy the 3.5" skinnies. I gave up and went with a 15x4 with a 185 tire which my local wal-mart carries. Actually handles much better with the 4" wheel and 185 tire than with the 3.5" wheel and 165 tire. Seems more stable around corners to me.