Where can i get the Iroc-z center

I need 2 center caps for my 87 Iroc-z i went to a GM dealer and they are $20 for one.

dont know if theyre cheaper..but go to thirdgen.org and check out all the ads on the top of the page
i know some of thoseplaces carry them, i just am not sure on the price

http://www.thirdgenresource.com/inc/pdetail?v=1&pid=543

Here you go, you can save $1!
I would give ebay a try first.