IMO, the best way for this to be done is for Tesla (or an aftermarket company) to offer an option for an expandable (collapse when you don't need all of it's capacity) refrigerator/ice box in one of the trunks.
It would be plumbed into the cars existing A/C refrigerant lines. With the huge main battery in the car, it could even run when the car's off, when needed. Great for those frozen items from Costco or the market that may need to sit in a hot car for many hours. No need to rush home!