I have a holster that has belt holes. The only problem with that is, that I have pants without belt loops so using a belt is not an option.

So here come my belt hole to clip adapters, made for a 40mm belt hole.
The part that goes into the hole is angled (see the model, I can not really explain it better) so it stays flat on the holster.
The two parts of the clip are held together by an M3x9mm bolt and a heat pressed M3 nut. I believe that it would also fit a 10mm and an 8mm bolt.
It requires supports, but they are pretty easy to break off. If you want to edit the model, feel free to adjust to your needs.
NOTE that all the files except the m3f is only one clip and it needs duplicated, mirrored and each split into two parts before printing!