@JMo25
Alaska Guide Creations has two different packs that integrate with their bino harnesses. One looks like a decent size that may work for you.
T&K Hunting Gear I think has some similar options to ACG.
Marsupial Gear has some options with bino harness and their bird bags which may work for you.
Kifaru has their chest rig and a hydro harness. The rig itself is more fishing focused but can’t see why it wouldn’t be fine for hunting, too. Downside is it’s probably not best for binos if that’s what you need. The hydro harness is more for a water bladder but you may be able to fit a little more or stuff a jacket into their external bungee webbing. You could always use another’s bino harness with their hydro harness if you’re after a bladder solution.
FHF ditto lots of the above.
Hill People Gear also has some good options. I don’t have any HPG stuff but I have been impressed with them, too. I’ve thought about getting one of their lumbar-esque packs that has great volume for exactly the use I interpret you’re asking about, especially since Kifaru dropped their lumbar pack options (which I hope return sooner than later).
The good thing about most, if not all, of the above is that they should work interchangeably when the components use 1” webbing and buckles. Of all I mentioned above quality/durability is there, along with customer service. The only manufacturer I don’t have direct experience with is HPG but I wouldn’t hesitate with them one bit.
Mountainsmith still makes lumbar pack options, too, which could work. Durability of materials—and unfortunately overseas manufacturing—isn’t going to be the same as anyone above, who generally use Cordura, but the dual delta straps will really suck the load into your back for comfort. That, with their straplets (an option) could work. It won’t work with another’s’ bino harness however.
I personally use an older lumbar pack with a bino harness for whitetail a majority of the time. It’s fine except when layers are needed. For treestand days in cold weather I often find myself needing a pack to layer up, or if a close stand I just take it easy on approach and open up layers to not get sweated.
I use an ACG bino harness but not one of their packs since I usually have a full backpack on for elk, so I can’t speak to their pack options. I did go with one of their bino harnesses with the MAX pocket and for them (and others) recommend it. The extra couple pockets allow you to keep essential items close (wind checker, knife/multitool, rangefinder, quick snack, lighter, etc). I’m in my bino pack all the time since it’s right there.
If you go the lumbar pack route, which again works for the majority of the time for whitetail, you’ll appreciate the freedom of movement and comfort they allow vs. an even a smaller pack. Smaller packs drag on my shoulders and don’t seat as well as a lumbar pack (for me this is exacerbated since I have a long torso). Should you go that route, just be sure to get a lumbar pack with a shoulder harness to relieve some “drag” and “flop” of a stuffed lumbar pack.
