Dunno how bright you want it but i’ve shoved 5mm LEDs into mini maglites before as an almost direct replacement for the bulb. From memory i cut the legs to size, made sure i plugged it in with right polarity, and had to slightly enlarge the centre hole in the reflector and might have even sanded down the reflector slightly for height because of a lip on the LED. Pretty straightforward stuff though if you’re up for it.