I just bought a Tenba Backpack for my winter trip to the islands.
http://www.tenbagear.com/products/2000_02.asp
I got the medium one, was able to fit:
Sea & Sea DX200 housing w/ Nikon D200
2 Sea & Sea YS-90 Strobes
Macro Port
UCLS Arms and Clamps
2 Strobe sync cords
16mm
18-70mm
60mm
External hard drive (notebook type)
Very thin laptop (very thin)
My wife carried on my Dome Port (in 2 aluminum cake tins) in her carryon.
Overall weight: 38lbs
It's a backbreaker, and I know that it's bad form to travel with the camera in the housing, but I'm more scared to check luggage than risk carrying on the camera in the housing.
It fit in all airline overhead compartments, including the small comuter flights.
It's very similar to lowepro, but with out the bulky straps, so it fits in small compartments better.
Take care,
John