Forgotten Fox: The timing of my advice will likely be too late as it's Sunday today, but you might need it another time.
Whereas we haven't needed to cool our
P4P+, I am experienced in keeping professional photography equipment cool (including the old colour transparency film). And other items. The simplest way is to use a large plastic cool box, available in any supermarket, plus several cool blocks (sealed in plastic bags to prevent moisture problems). You'll have enough space for a drone and batteries and it's an inexpensive solution that's also simple.
Make sure your cool blocks are fully frozen before use. It's easy to underestimate how long it takes to get them to maximum performance. Also, there are super-cool blocks available that will - for example - turn a can of Coke into slush or an almost-frozen state. These blocks take longer to fully freeze. We use a combination of both normal cool blocks and one or two super-cool blocks.
Cover the cool box with a folded blanket in the car to keep sun off and to provide additional insulation.
Open car windows whilst driving.
I've worked for many years in Sudan, plus South Africa, and in the outback areas of Australia - so I know what "hot" is and how to counter extreme temperatures.