This is my Lithium Coin Cell powered LED lamp box. It is made from the free web program Tinkercad. All you 3d Printer People have probably heard of it. It was printed on a ThingOMatic MakerBot.
Basically it has a coin cell battery and a magnet. It was made to safely contain an LED.
Tape an LED to a coin cell battery and stick the battery end to the bottom of the box. Then tape the lid to the box and put the magnet on the outside of the bottom and viola, youre done