Current Carry: Skookum Dog Citizen Canine prototype, Founder's Briefcase (every day carry), Small Cafe Bag (every day carry), Shop Bags (groceries, extra random stuff), Aeronaut 45 (travel), Synapse 19 (day hikes), Smart Alec (longer day hikes), Skookum Dog Road Duffel (Medium) (travel), Clear Organizer Wallet, Travel Stuff Sacks, Organizer Cubes
The CoPilot works well as an iPad briefcase.
(Oops -- didn't realize you were looking for a bag for a 13" computer.)
eBay. According to the Introducing the Cadet Briefcase thread this size Cadet will fit the 13" MacBook Pro, but not with a cache, I'll quote one of the posters, ShineAgain, since TapaTalk won't allow links to individual posts, and the thread is quite long:
moriondI have the smaller Cadet, and my 13" MacBook Pro fits in it just fine. It won't fit; however, in a sleeve. I've hauled the thing back and forth to work without any problems. It's padded on the front, back and bottom, just doesn't offer much protection on the sides. I also carry my iPad 2 in the sleeve right next to the MBP, and there's plenty of room and protection for my comfort.