As an aside to the above comment: great starting point for sure. HPG kit bags are great. I have a HPG SAR bag and it's great for carrying a weapon and some other stuff. Lots of crap, actually. I've used it for fishing gear with a pistol, survey equipment with a pistol, note-taking stuff and cell phone/camera with the pistol... various iterations. I want to carry my binos inside the bag with the iron (usually a Glock 17+ extra mag), but they're too bulky (10x42, so not huge).. And it's way too bulky to wear a separate harness over top. I usually keep the binos near my hip or just stowed in my pack, since the vast majority of the time I'm not using them unless I've stopped. The pistol is not a bear defense gun... its for people. If I got into a spot where I needed it (the bag, changing out to an acceptable weapon) on a lion hunt or running into a bear bait, or checking traps, that's another great use for it while wearing a back/framepack, but it's not ideal for the OP's intended purpose, where he's asking for 2 separate things... but I had to share. And, of course, the more ish you stuff into it, the more strain on your neck/back by the end of the day. I would be absolutely lying to say that it's perfect and stays put at all times, but it doesn't. Less gear might make it better, but I just have to have some things up front, rather than stowed.
That said, I have seen a lot of guys run a lot of setups and I still am not convinced many of them are practical from an accessibility perspective, nor comfortable. Some, yea, but not all. One that stands out in my mind is the gunfighter style (a few different versions out there now) under a dedicated bino harness. The position of the grip needed to be adjusted a bit for smoothness of draw, but I have seen where guys have simply added some foam/padding to the backing on the kydex against their chest to get the angle right. I'll reserve judgement as best I can until I do some more digging and test some out. I love the idea of the Diamond D, if it can realistically be worn with a bino harness and a pack with a substantial hip belt.
Intrigued to see what others have to contribute that hasn't already been discussed here or elsewhere.