How about one of those units that when the car is not running, the licenxe plate, light and all retract under the car. Counld only see the license when the car is running. They work off of an electric motor I believe. Have seen several, but never exaimed closely. I considered one for my DeSoto, but decided to recess in roll pan with a very small light. Does not take much light to illuminate a license plate.

Jack