I recently purchased a TwoTrees TTS-20 Pro laser engraver/cutter. It was a deal from the manufacturer, one of the final sale “return” sales.
Sadly, it was missing many pieces, including the focus tool to help focus the laser against your material.
 

I reached out to a hobby group and found someone who was nice enough to give me their measurements and I modeled my own.

Hopefully, no one else ends up in this situation, but if they do, I hope this helps.