I’ve got one of the usb battery bricks and a 26800mah usb power supply/bus board that I picked up from modular addict.
It depends on what you’re running, but a 3 sis, cold mac, rings, Pam’s, and an o&c run for at least 4+ hours and a few phone full charges for a weekend away from the studio with plenty of bleeps and bloops.
The build on that power supply is very much doable, it’s all through hole and doesn’t take much time at all. I do suggest doing yourself a big favor and buying keyed headers for it. I also cut mine down to just 5 outlets to better fit into a very small pelican case.