This can be printed using a filament swap or just single colour as you're probably going to be painting it anyway. I printed at 0.12 layer height as it's quite small (70mm x 20mm x 20mm) and I wanted a cleaner look. 

I used a single led chip from a cheap 5v strip but any 5v led will do. Its a simple matter of stripping the usb head back, soldering the black and red to negative and positive respectively and hot gluing it all into the torch. The led wants to sit about 50mm from the bottom of the torch. 

This can be used on any USB wall plug charger or on a USB battery pack. If you're using a battery pack, there's not enough draw to keep the pack alive unless you have a “dumb” one that doesn't have the auto sensor. There's also plenty of videos out there to make your own from an 18650 battery if you're that way inclined. 

Post your makes and have fun!