I decided to install 12V outlets in place of the useless (to me) cable outlet to avoid cutting the cabinetry in a visible way. An oversized nylon blank switch plate cover will fit into the space nicely and has room for two outlets. Use a hole saw on them. The luan underneath can be cut with the same saw and anymore cutting can be done with a fine work hand saw. I used a dual Blue Sea outlet, similar to this single outlet.
What I liked about it is the mounting plate can be put on from behind and used to hold the switch plate cover tightly to the luan making room for two outlets. Two outlets are tricky to install without covering the screw holes.
I also tapped into the fridge circuit for power, something that is easy to do on A-frames with a fixed bed. Because the fridge circuit is 20 amps, I ran 10 gauge wire to the outlets and put a 15 amp fuse to protect each one.
Others have been successful in using the radio circuit. My thought on that is to make sure to watch the amps. IIRC the fuse for the radio is in the cabinetry and the microwave has to be pulled to change it. Again IIRC, the thermostat is powered by the same circuit, so if the fuse blows, the Coolcat and furnace won't work. So at least check out the fuse situation so you will know how to fix it at camp.