At REI the other day, I found this thing from Eagle Creek called the File Cabinet or something like that. It was basically a collapsed, thin, stiff thing for holding tabbed folders and similar rectangular stuff. I really need something like this for my messenger bag, but Eagle Creek is just... not cool.
I figured Tom Bihn must have something like this, and lo and behold, there's the Freudian Slip. But it's vertical! I would suggest that backpacks need this kind of filing help less than swooshy messenger bags do.
Tom Bihn, save me from Eagle Creek!