To to check the availability of domain names in very large quantities?

I have keyword lists in the thousands, and would like to check the availability of multiple extensions for each of those keywords. But the limit for tools like the Godaddy bulk tool is 500 domains at a time.

My Godaddy account exec has an internal tool that will allow him to check an unlimited number of domains, but obviously this takes some time as he has to get back to me.

Are there any tools out there which can check domain name availability in such large quantities, without the 500 domain limitation? Commercial tools are OK, it doesn’t have to be free. Market Samurai has a domain checking feature but it seems to be limited to 200 domains or something like that.