You didn't say how big a pack you wanted. I'm guessing something more than a weekender?

I've always liked Gregory packs, though I don't know of any with the features you describe. I've also found REI gear to have tremendous bang/buck. Several of their packs feature dual top-loading and U or J-shaped zippers for duffel style loading. This might be something you'd be interested in. Look at the REI Mars and Venus packs.

Kevin B.