Take a look at MPCs, should be able to find some nice ones in that range. Here is one that probably won't stay under $20 though... http://cgi.ebay.com/STUNNING-5-C-54...160?pt=LH_DefaultDomain_0&hash=item2eb13dbde8
Bloody H*ll, take a look at varieties. That market is so soft right now that I've literally had Wexler Top-100 RPM varieties in GEM condition not get so much as a watcher at .99 cent starting price and .99 cent shipping. And I have decent photos of not only the RPM, but also the die markers!
Mpc,s for the most part are very inexpensive in raw condition and that can be said For some common graded ones as well, i have a nice selection if your interested