In reply to A Longleat Boulderer:
I've never used one but the Macpac Minaret has many fans and would fit the bill. As would, at a slight weight penalty but with greater space, the Macpac Olympus; and I have one of these myself so am happy to make that a personal recommendation.
Mine is over ten years old though, so there's always a chance that current models aren't made to the same bombproof standard.
T.