Kifaru made a couple of larger lumbar packs and will occasionally rerelease them- the Tailgunner and Scout; they are large enough you definitely want small shoulder straps with them- I've owned both, both are the highest of quality, have plenty of room, carry well, but in the end I always go back to daypack
I do see used ones for sale relatively often
the HPG one looks pretty good too, but remember it needs a belt to go with it and I'd highly suggest shoulder straps as well
