i don't have any packs for sale, but I can offer one potential suggestion for about $100 or less:
Military Molle packframe and bag are available on ebay for as low as $65 or less, then add a Wilderness Specialties meat hauler accessory (about $25), which attaches to the (plastic) military packframe underneath the packbag.
You can quickly and easily detach the packbag to use the meat hauler.
Added benefit - these packframes fit in most packing panniers, in case you're using any pack animals on your hunts.
No dedicated rifle-hauling system, but you can hang your rifle sling on the top of the frame while hiking, or for a better set-up, attach a short piece of dowel or small-diameter pvc pipe to the frame's top corner to create an even better rifle-sling hanger.
Not the lightest set-up out there, but durable, user-friendly, and inexpensive.
Good luck with your search.