A 15-liter compressor fridge that runs on 12V. Fits a case of water, leftovers, and insulin or meds if you need them cold. Quiet enough for the bunk. Low-voltage cutoff so it does not kill the batteries overnight.

Removable basket, interior light, and a handle so you can take it into the house on home time.

30-day road test. If it will not hold temperature in a hot cab, send it back.