Have you tried Findology?

Findology is a pay per click search engine network that serves two
billion searches per month. You can bid a minimum of $0.03 per
keyword phrase, and Findology also features automatic sign-up approval!

If you deposit $25 into a new Findology account through this promotion, you will receive a $75 credit for your campaigns. That's $50 in free credit! This is a great opportunity to test some of your Google campaigns that have experienced a drop in ROI due to keyword cost increases.