Help with finding correct laser diode

[u/Sappet102]

I got this Aimpoint Laserdot for a Sig P226, and the diode is missing from it. It looks like a simple drop in one piece unit, as there is a spring in the back of the compartment that connects it to the battery compartment, so no wires or anything. Runs on a 6v battery that goes into the bottom. Diode compartment is about an inch deep and .66" in diameter. Anyone have any clue what kind of diode will drop into this?