Take a look at Recreation Equipment, Inc., in Seattle. It's a membership co-op which has outfitted successful US Everest climbs in the old days.
I bought the Aluminum frame which was meant for multiple bags, hauling from one camp to the next.
Have to edit. The Kelty 65 in the link that Jared posted is like mine but mine is full length. Hindsight says that 65 would be wonderful.