What's up Drac- pretty much all power banks are 5V, so really you'd be good with any one- just focus on finding the biggest mAh rating (juice) in the SMALLEST shell/ package. It has to fit in the grip section, which you can always measure in the saber you're using, then just look at specs of power bank and it'll show dimensions. You want one that's at least 5000mAh IMO, especially because they exaggerate the crap out of that rating lol.
It's actually really easy to do

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