My solution has been to purchase a Lowepro dryzone 200 for the camera gear (to keep the non-waterproof stuff dry) and a separate Lowepro Nature Trekker for housing/ports/strobe. This is more aimed at local travel rather than airline travel in my case. It seems like a good setup to me, but I haven't field tested it yet.
BTW, I've travelled extensively with the Nature Trekker in the past as carry-on, and although it's slightly too big for this purpose technically, I haven't been stopped from taking it onboard a plane yet.
