I found that it was very hard to source a light bulb that didn't overpower the designer lithophane moon lamp washing out the lunar surface detail in the process .

This diffuser is intended to slide over the top of a Philips 9W 900 lumen LED light bulb (BR9T50c865NC) to absorb some of those lumens evenly.

The bulb has an external diameter of 50mm and a height of 40mm.  Fusion360 file included in case you want to adjust it to fit a different bulb.

The internal diameter of the diffuser is ~52mm.