This is a spherical light source.

It's an additon to "RLW Lightpainting Tool Adapter Kit" .
https://www.thingiverse.com/thing:3016474

Gives you a spherical light source together with Hole_16mm_Tool_Cap_40mm_V2.STL from the adapter kit and flash cap connector to your flashlight.
See https://www.thingiverse.com/make:534706

IMPORANT: Use no Infill, 2 perimeter and 2 layers on top an botton.

If it works right you get a hollow sphere with a flat wall to the flashlight to diffuse the light.