I'm very interested in a retro-fit seat cooling device. I found some sites with some interesting stuff.
One is a seat cover that has tubes and a circulating pump.
https://cooldatazz.com/
Another is a Youtube from a guy with a good How-To on fabricating a Peltier water cooling device.
And this is a guy who broke into a high end car heat/cool mechanism.
Probably not this summer but I'd love to have something for next summer.