I modded two or three of them way back when. Just remove the reflector and bulb and replace with a Nichia. Pretty much pressure fit into place, I used a piece of heat shrink over one of the leads to prevent shorting. One lead to the copper "switch" and the other to a small copper or brass square - used as a battery contact. Solder another wire from the other side of the "switch" to another copper or brass square to make the other battery contact. I use 2 2032 coin cells stacked together, they will stretch the case a little but give a little more run time. 1632's will fit better but you might have to use foam to keep the contacts in place. There are at least two different styles of ZipLight innards that I have run into, mainly a different switch design and both modded fine, just trim out whatever gets in the way!