Yeah, I did something like that way back. Small piece of perfboard with 3 or 4 clear red 5mm LEDs, soldered in parallel, small on-end ballast resistor in the middle to not suck down too much current, and 2 “legs” out the other end to stick into the teeny holes on the plastic doodad the regular bulb sticks into.
Worked okay, but never really needed red light, so no idea where it even disappeared to. Hope it wasn’t with the alkaleaks inside, else I might as well just toss it if I ever find it. 
Those teeny little LEDs, I wouldn’t DD them, as they’d likely just pop after a while. Across a coin-cell, like for a throwy, fine, but not from a pair of AAs.