Any charger that can supply at least the current that the device needs (at 5 Volts) will work. It can't supply too much current, because the device draws the amount of current it's designed to draw. (My "charger" is normally a 30 Amp 5 Volt supply - I don't have any devices that will draw 30 Amps.)
I'd buy a decent one, but the one I bought on Amazon for about $5, to charge batteries that were removed from the phone, has been working for years, and it's a better charger than any that come with a phone. So go into Best Buy, find one with a name you recognize ("Joe's" isn't, "Motorola" is) and a price you like, and sufficient output current, and it should work.