Haven't tried it myself, but this looked like a possibility, for me anyway. May drop the pistol just far enough under the pack belt to be out of the way, but not halfway down your thigh like the typical "tactical" leg holsters. They have chest holsters as well, but I generally have binoculars and a range finder there.
https://gunfightersinc.com/shop/micro-aggression-thigh-panel/Thought you might have found the holy grail there. Still might be an option except for the leg tie. Leg ties are good for not very active duty roles. Running with one on doesn't work and after hiking all day with that thing around my upper thigh I guarantee I'm going to have blisters where I shouldn't. Might work if the dropleg straps were rigid so you could pull the gun out without the holster coming up with the gun. It's a good start though, I like the idea of a dropped holster.
