If you're that worried about temperature, why not cut a small hole in your Air conditioning duct (assuming you have A/C in your car - in Florida it's like required by law or something ) and shunt a small tube onto the cage. You might have to worry about condensation, but that could be circumvented (get it?) with a small trap in the tube.
Just an idea...
Jason

_~= Dearing =~_
"WAY too happy about having #99."