A bit more research: I determined that the general category of pack I'm looking for is "panel loading", as opposed to the more common "top loading" that I'm used to. From what I've seen, I'd need it to be larger than I would for a toploader (which is fine by me; as stated, I'd gladly take extra weight for better organization).

Upd: Two packs that look like reasonbable approximations are the Granite Gear Nimbus and Stratus Latitude. You can pretty much fillet them right down the middle My only concern is some of the reviews report some sweat issues with them in hot weather. Still, the reviews tend to be very positive.

Well, at least I have a couple of good-looking choices, even if they do have their weaknesses.