I have no running water in my vehicle.

My experience with these is in hydroponics.

They don't overheat with water all around them and they last a very long time with no maintenance and are cheap. They draw minimal power and can pump hundreds of gallons an hour for years at a time. Just let your water run down to the point that the pump is still covered and then call it empty.

Personally I have used these active aqua pumps the most as that is what is sold in my local hydro store. https://www.amazon.com/Hydrofarm-Active-Aqua-Submersible-Water/dp/B0049XENYS?ref_=fsclp_pl_dp_3