Is there a Cheap but good Satellite navigation system i can buy when visiting the East Coast? Can i rent one?

If i was to buy one will they come with all the states? Would i be able to use it when i come home to Ireland? How much should i spend and what makes should i avoid? Thanks|||Most of the large car rental companies (Hertz, Enterprise, Alamo) offer vehicles that have the navigation system in them. Before renting/reserving a vehicle I'd e-mail them or call them %26amp; make sure that that is something they offer.