Sorry for resurrecting an old thread but Timbuk2 sucks.
I went to the Timbuk2 store in SF this afternoon and asked about ordering an extra small messenger bag with a stabilizer strap. They won't allow it. The snotty clerk told me nobody would ever ride a bike with an extra small bag. I told him I would.
I don't get it. I know it's easy to add a D-ring, but I don't want to have to DIY with a brand new expensive bag. If their extra small isn't for riding, why do they bother making it with the cam-buckles?