3. Fits a MacBook.
Bonus points for it being visually interesting, or for finding one of those Japanese briefcase-backpacks. I had a Sailor Moon one once. Loved it.
And yes, I know there are tons of cute messenger bags, but the fibro exacts a toll for not distributing weight evenly. Even a regular purse results in the body getting out of alignment and giving me those fun waves of achiness. Is why I use the little red backpack.
EDIT: Why not just get another Obus Forme? It only has a one-year warranty, and I am apparently hard on my backpacks. So yes, this is an item that I am willing to splurge on, if it means the kind of quality that means I don't have to buy another backpack in two years.