My 9yr old son designed this. Its a plastic grenade that you put an LED in and connect to a standard CR2032 watch battery. He used a Blue LED on this one, but you could try 'Toxic' Green
or even UV. We've printed this in black (disaster) and Glow in the Dark Green ABS plastic (OK) and found Clear PLA the best.When you've printed a few of these off you are obliged to run around your house throwing these at each other. Of course, you are required to make the appropriate Nuclear explosion sounds. Don't forget to practice your 'death throws'
I've attached a standard .STL file for printing on pretty much any 3D Printer. Once printed you just need to glue on a 2032 holder; chuck a 2032 cell in it