Have you tried Findology?

Findology is a pay per click search engine network that serves a billion searches per month. You can bid a minimum of $0.01 per keyword phrase. That is only one cent!

If you deposit $25 into a new Findology account through this promotion, you will receive a $50 credit for your campaigns! This is a great opportunity to test some of your Google campaigns that have experienced a drop in ROI.

Get more information here