I forgot I have a Black Shark Fun Cooler 3. I used it when livestreaming in summer and it worked. It used about 30 watts.
Video here:
It is USB powered
Nice cooler, if you have the right application, and don't mind your phone using over 30 watts of power!
Dashcams don't produce much heat, the problem is that they sit in the sun at 90°C+ ambient air temperatures, making it hard to get rid of the small amount of heat. For an under-seat dashcam, you probably don't need any active cooling, because even in Oz, it is never going to be in much more than 50°C ambient temperature under the seat, as long as there is air movement around the device.
For any dashcam, all that would ever be needed is a small fan. The real problem is in obtaining a fan that will work reliably at 90°C+, and will not be heard by the microphone. Most fans are not designed to work at 90°C+, the bearings fail, they are unreliable.
The alternative answer is to make the dashcams more power efficient. Processors do keep getting more efficient, but then we keep asking them to do more; more resolution, more HDR, more AI, more channels...
So, instead of a single 4 channel dashcam, it would be much better to have 4 single channel dashcams, all recording to a central network file server locked up in the glove box. Viofo's A229 remote cameras already encode the video in the remote cameras, so it wouldn't be a big change, use wireless communications and it would be an easy install...