I recently bought a Tamrac Summit backpack. I haven't tried it with the Hassy kit, but my 5x7 Korona fits nicely in it, with some holders, meter, reducing back, and a couple of lenses. It would hold a pretty extensive Hasselblad kit easily. I use strap on external pockets for the holders.
It's very nicely made and comfortable to carry IMO. Well padded, stands up on its own, very flexible partitioning.