I have tinkered with this a bit. I use an external frame but maybe the information will be useful to you. I molded a kydex mounting bracket that screws on my frame (Kydex is stupid easy to mold). I hand made a crappy bag for the side of my pack into which my holster projects. It now rides upside down on the frame in a little bag attached to the pack body that has a weak elastic seal about 7 inches from the bottom of my pack. High enough to keep it out of the dirt. To access it I reach straight back and slip my hand inside the crappy bag I made, the handle of my pistol is right there I simply pull it straight back toward me. It is a Little difficult to place it back in the holster as the elastic flap gets in the way (I wish I were a better seamster). The bag does a fair job of keeping it from getting banged up when I walk through brush or fall on my ***.
I have also made a rig to hold a Marlin 1894 and an AR15 carbine too but have yet to fashion an enclosure for them for I lack the sewing skill.
I have also made a rig to hold a Marlin 1894 and an AR15 carbine too but have yet to fashion an enclosure for them for I lack the sewing skill.