Need reliable proxy - slow and steady is fine, as long as it's steady

I've been trying to mine a particular site, and just got shut out. I was trying to do all the right things -limit request rate, etc. I still need to make a few thousand more requests before I've got everything I need. What's a proxy site that can take me the rest of the way? Preferably for free.

I'm new to scraping, so if there's anything else I can do, please suggest away!