GearBest offers the Huanjie 12-volt 12-Can Portable Car Refrigerator / Warmer for $22.99 plus $1.52 for shipping. That's $8 off list and the lowest price we could find. It features 7.5 liters of capacity, 12-volt "cigarette lighter" power cord, carry strap, hot/cold switch, and magnetic lid lock. Deal ends June 21.
Note: It ships from China and will arrive in two to five weeks.