How about $160 + $13 shipping + Tax?
http://cgi.ebay.com/ebaymotors/A-C-Compressor-1998-2003-Chevy-S10-GMC-S15-Isuzu-...
That one is for the 2.2 Liter engine. You can probably find others on the
Web. I don't have any connection or experience with any suppliers including
the one above. Of course, first you'll want to verify your compressor is
bad.
You'll want to stick with the newer R134a refrigerant. Even if you could
find a older compressor, rebuilt or in good shape, and could figure out how
to get it mounted in your pickup, it would have been designed for R12. You
might be able to use it with R134a, I don't know.
Some people think compressors don't last as long with R134a as they did with
R12. Other people, like Grumpy, think that the newer compressors are just
made cheaper. If I had to bet, I'd go with the second theory.