Someone is offering a script to block proxy sites from accessing your site can see the main site here

Proxy Block Script - Home - PHP Proxy Block Script lets you stop Web Proxys like PHPRoxy Glype and more websites and ban the ips

and here is the demo url you put in your proxy to try and visit.

Suppose to work against any proxy script worked against every site I tested so the ability is there just not used as they wouldnt make the money they should