This is an adapter for the "quantum" brand LED flashlight sold at harbor freight. The one that runs on 4 AAA batteries and dies in about 20 minutes. (harbor freight sku 63934) It would prob work on other flashlights that have 4 AAA's in a plastic tray. Takes 30min to print so give it a shot.

Printed in PLA on an ender 3, make a conductive bridge between the tailcap and the body with aluminum foil to complete the circuit and actually make it work. Or print it in some sort of magical conductive filament. That could work too.

Turns out this flashlight is stupid bright on just one 18650, and I'll bet it lasts longer than 20 minutes.