From my camper notes:
Far infrared ceiling panels, made in WA: https://www.heatinggreen.com/product/solaray-heater/
Research Far-Infrared Heating mats from companies like Arkon in Canada and WarmUp.
I also considered embedding these in a ceiling, floor or wall to create levels or zones of heating. Depending on the heating load, battery state, plug in availability, etc., you could choose which panel(s) you wanted to activate. Due to the lack of floor space in most small campers, radiant "floor" heating does not make much sense. https://www.thermosoft.com/en-US/radiant-under-floor-heating/for-laminate-engineered-wood
Thanks for the links, now if I could only find it in 12 volt.