I have an old Mountainsmith lumbar pack I got in the late 80's. It's very comfortable to carry, has straps to tie on jacket, pad, etc. and expands a little. I like to use it on short hunting trips, and used to take it on occasional minimalist overnights.
Mountainsmith, REI, Cabela's and several others make quality lumbar packs that should do what you want. shop around and find one that feels good on you and go with it.
And yes, the suspenders are vital to carrying any load in them.