Walmart offers Tomshine 7.5L Car Refrigerator for $35.99 (reg. $71.98) free shipping.

Product Description:
2-in-1 cooling and heating design - it can be used as a fridge or a warmer, serving multiple purposes, great for cooling and keeping warm of lunch box.
Thermal insulation system - employ the semiconductor refrigeration system, combined with thicker structure, providing better insulation.
Easy to use - one button operation to switch between cooling mode and heating mode, and comes with a 1.8 meters power cord which is long enough to reach car outlet.
Large capacity yet compact size - it has a capacity of 7.5L, which can hold 9 bottles of cola（330ml）, but the whole unit won't take much space of your car.
Versatile use - essential for a road trip, also great for barbecue, fishing, camping and more.