Anything normally powered through USB is 5V with a maximum 500 mA current*. So anything with that specs can be used as an alternate power source.
Note that it has to be 5 Volt, but the current rating could be higher. The circuit will not be “charged” with a 3A current if the power supply rating says 5V / 3A. That only means that the power supply can deliver a current of 3A.
Something like if you buy a $5 item with a $100 bill, you will not be charged $100, just the $5
* There is USB equipment that has double connectors, and that is simply because the total current need is more than 500mA.