Google Maps – Display Circle with Radius of N Kilometers from Specified Place

BatchGeo is a good place to start. You'll need to look at their Spreadsheet Template to make sure that you're importing all the information you'll need. The Store Locator function is what you're looking for.

This is a comment by the Google Maps Team to one of their posts on G+:

Location services ("My Location") works a little differently in MapsGL right now but you can still use it. If you're getting directions, you can still use "My Location" as a starting/destination point. Your browser should ask you if you'd like to use a "rough estimate", which is usually pretty accurate. Try this out in Chrome and see if it works for you. You don't need to pick between MapsGL and the "My Location" feature! For anyone else interested, I'm referencing this feature announced a few weeks ago -- http://goo.gl/OJoEK