I need a whois source that will allow data to be scraped without there being a limit on how many free searches can be carried out before the site blocks access, limits what data is scraped or has registration/access requirements that might cause the script to fail completely.

I've had recommended to me this site - http://whoisxmlapi.com/ the API for which allows unlimited searches but it's a paid service so before springing for it I was wondering if anyone knows of another better option?