Has anyone invented solar powered air con yet?

Is there anything out there to keep my car cool while we are stopped? This does not mean I want to leave them in the car routinely, but there are unexpected situations when you need to - for example if you're stuck in a traffic jam on a hot day or even just a way of keeping the car cool so when we get back at the end of a walk it's not boiling hot. Maybe an air condition unit which is solar powered? Does such a thing exist? What do the police vans use as there must be times when their dogs have to remain in the vans?
Beate Rothon