power outlet placement

My husband and I travel across the country 2x's a year and have a cooler that plugs in the 12v power outlet to carry our food and luncheon materials. When we want to use our hand held GPS or charge our cell phones we have to keep unplugging the cooler.  Also if we want to bring anyone with us there is no room as this cooler takes up a third of the back seat. It would be great if a 12v power outlet were put in the trunk so the back seat would be freed up for other things.