How far is the drive, and are the newts fully aquatic?
When I had to transport large cold water fish a 3 hour distance, we would have a painters bucket in the back seat with a lid loosely on filled about half way, and we would attach an airstone to a car adapter and plug it in to the charging port. Then I’d just keep the ac on to try to remain within the proper temperature. I’ve also transported aquascaped tanks short distances by removing the fish and putting it in a tupperwear similar to what they come in at the pet shop, draining 3/4ths the water and covering the top of the aquarium with plastic cling wrap to keep the plants alive.