For years, the prop community has considered the Heiland flash to be the correct flash gun for Darth Vader's lightsaber. The Micro Precision Products (MPP) Microflash was used for the hero version of this prop in ANH.

Converting this into a usable prop replica is extremely easy, aside from actually finding the MPP.

Here are some notes about placing the rubber grips. If you're looking at the flash from the rear with the bulb release facing the 12 o'clock position, place the grips at the 1, 3, 5, 7, 9 and 11 o'clock. The ends of the grips should be cut to a 45 degree angle to match the screen used prop. The calculator display bubbles should be displayed at 7 o'clock.

Aside from the MPP, all of the parts listed above are available through Blast-Tech.