The way I would do it would do it is to run a a cigarette lighter extension from the 12v socket on the dash.You could hide the wire by running it down the middle next to the seats and under the back seat to the rear compartment.You could tap into the 12v wires powering the rear lights but you would have to find a way to remove the inside panel to locate the wires.I think it would be a lot of work just to run your cooler presumably for temporary purposes.