This is the printed portion of a leg drop system I made...essentially just drop nuts in the 9mm holes and screw them all together with an M5x30 or 35 screw.

The little box with a slit in it slides over the the system as a locking mechanism and the weight of the gun keeps it secure....if you want it to be more secure just glue the thing on there but i have it set so you can remove the holster itself.

In your 3mf file (or using autodesk files) just take that little box and push it into whatever your holstering and then you now have a leg drop holster.

The two sits in the drop down bar are meant to be connected with soft cord like nylon or elastic....it just needs to support the wight of the gun...and then use the same strap material for the leg strap slits as well.