Script to detect IP city location and redirect to third party website by jimmysoechting

I need a script to detect the IP city location of a visitor, and then redirect them to a classified ad site in the city they are in, so if the classified site for example was backpage.com , it would detect the IP location of Los angeles, and redirect them to losangeles.backpage.com… (Budget: $30-$250 USD, Jobs: Anything Goes, PHP, Software Architecture)