Here is a quick print for a P21 light (12V light used in cars) Using a bit of 220V electric wire (copper, strong, 1.5mm2), I was able to make a spring for the bottom so that the light stays in contact Please be careful and use at your own risk : these lights may become quite hot. Be sure to take extra care. (these light may be used when a load is needed on a 12V source, i.e. custom ATX bench power supply, hence the socket to be able to replace it easily)