Directory Questiosn

I have a client that helps a LOT of people. He owns a great non-profit agency and is looking for a plugin that can list government assistance/non-profit agencies nearby according to the user’s location. I can either have the location be a drop-menu and has a selection made, or some sort of GPS for the user’s location….my question is would I have to add in all the agencies by city/state manually, or would I be able to embed a type of 501c3 orientated database with this plugin?