An approximate of the official Fenix diffuser. I printed it in Glow-in-the-Dark filament with a color change at the end.

This may fit on other Fenix Flashligts like the PD35 or some sort, but I don't own them to test.

I've included the Fusion360 file for you to mess around with. You can try changing the WallThickness parameter which is currently set at around 2mm.

Print instructions

Print in provided orientation.
I used a brim.

If you're feeling that color change that I did, you just have to do it after the lip of the support struts.