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I salvaged a 3V LED driver circuit from a flashlight that took two batteries. When it lived in the flashlight, 3 LEDs were soldered to a triangular circuit board. I removed the circuit board from the flashlight, and soldered a black wire to where it used to connect to the negative terminal of the batteries, and a red wire to where it connected to the positive terminal. I also unsoldered the LEDs and soldered a black wire to where the negative leg of the LEDs used to be, and a grey wire to where the positive leg of the LEDs used to be. Afterwards, I wrapped it in a strip of newspaper and dripped wax over it to give it padding and insulation as well as to make it waterproof. That last step probably wasn't necessary, and will prevent the circuit from dissipating heat, which may reduce its lifetime. This particular circuit is fairly effecient, so it doesn't generate very much waste heat. My friend reports it still works great after three months of using it several hours most nights, so the wax and paper coating may work out. The important part is to put some insulating layer between it and the base to prevent a short circuit (assuming you use a pumice base).