Thanks William. I am not referring to the regular external power supply (the one you mention looks like a laptop power supply).
I am indeed referring to some sort of power pack or battery supply pack. As I mentioned, someone in the Amazon review section mentioned using one of these with one if these boom boxes. The person who posted did not go into specifics about what they were using (32000mah power supply was all that was said). And they didn't address someone's specific question asking exactly what this was, so I was wondering myself if this was real or not.
So I don't know if this can be done. I was imagining some sort of power pack that you plug into the AC to charge up, and then unplug and bring with you to plug into your other devices, giving them power for some time before you need to charge the power pack back up again.