My buddy is fixing up a van to travel around the country in. He asked me if there was a powered travel humidor. I had not heard of such a critter, but I told him I’d pose the question to y’all.
They have ice chests that run on 12v may be a place to start. Unless he's gone months at a time shouldn't be an issue, the vehicle has to be comfortable for him so should be comfortable for the cigars.
I think he'll be fine, just keep lots of charged Bovedas handy and keep the vehicle comfortable. You probably won't be camping in Oklahoma during August or Alaska during January.
I havent herd about anybody using them but aren't some of the 12 VDC travel fridges (like the one above) thermoelectric??? that would work if the hey had the right thermostat , toss in some Bovedas and done!!!!
But as @Boudie said if temps are not extreme ther might not be a need for anything but a good sealed cooler