When I installed my LED strips, I hooked them up with a Milwaukee M18 battery and one of these adapters. (there might be better/cooler ones).
I have a power station and everything and I still use the battery out of sheer laziness. I usually use my lights on a dim setting for ~1 hour at a time. I can’t remember the last time I charged or checked the battery. If I was out at night for long stretches with the lights on, it would probably be different.
Just spitballing, but you could consider getting a small solar panel (I’ve never used this one and I’m not sure if it’s big enough, just an example) to charge your USB power bank (maybe Anker makes one), and installing it in the back window if you have one. Then it could be all self contained inside the camper shell.