Find the WAN Ip not Router IP

I'm trying to find a way to find the IP of users. I want the IP that their ISP assigns to them. if you use request.userhostaddress it returns the router IP if behind a router.

There has to be a way to get the IP assigned by the ISP because sites that check dns info and clock connection speeds can get it, and i also saw on another forum where a guys signiture showed my WAN IP address, so it can be done but i can't find anywhere where it's done.

Any ideas anyone???