Can you mod flashlights coryochoate?
If so, you can try do something like this:
Use a Jaxman host, a 18500 tube, make some internal modification to make it a triple and to use a 18650 battery.
It is shorter than a BLF A6 or a Convoy S2+ or even a a Jaxman E2L, and it will give you enough power from the battery, as it will use a “big one”! Just an idea 