Filter page visitors by zip code

I have a home appliance repair service organization, and also I’m mosting likely to begin using registrations. Given that i can just approve customers from the locations I solution, prior to touchdown in the registration web page, I require a method for them to enter their postal code, and after that be rerouted to the proper web page. Exists a plug-in that supplies a comparable attribute, or can any person offer me any kind of instructions on just how to apply this.