Why are you worry about battery drain if the car is being driven? Having those lights on for 30minutes to an hour during loading/unloading should not drain the battery. If the car is running, the alternator will power them, thus no worries for battery drain. But if you must turn off those light, just use a screw driver and insert it into the hatch's latching mechanism causing it to lock and therefore shutting off those bootlid lights. I've used this trick quick a few times when I need to keep the hatch open for hours.