This is probably better as you aren't relying on Amazon's API. Scrape every product, get all the sellers, then start flagging each seller as valid or not. Amazo

This is probably better as you aren't relying on Amazon's API. Scrape every product, get all the sellers, then start flagging each seller as valid or not. Amazon won't really be able to shut you down. Even better is once the extension runs on the users computer, you will be able to scrape using your customers which makes it harder to block. This looks like a great idea.