Some accessories are just better left to other manufacturers, although years ago I did get (as a mail-in promo) a laptop bag with an Apple logo on it for my PowerBook 520c. It was a pretty good bag. I sold it separately from the laptop, got a lot more that way.

Carrying bags are pretty personal choices as far as regular briefcase-like bag vs backpack vs messenger vs sleeve inside an existing bag. They do carry bags at the Apple Store, although perhaps not too many. Surely they didn't answer your query about bags as no, Apple doesn't make them, and leave it at that. Would be pretty stupid, and if you get that kind of service from that store location you should definitely feed it back to Apple as they do care about having a reputation for good service there.

I generally like Eagle Creek stuff, but I have to say it worries me that it's designed for 12-17" laptops. Too much size variation. I like having a bag designed precisely for the particular laptop size. I have a Brenthaven messenger bag for my MacBook Pro: http://www.brenthaven.com/core-protection-levels.html But apparently messenger bags are on hiatus for a couple months while they redesign. These may be worth a look in the 13.3 inch size http://www.brenthaven.com/catalog-sleeves.html Just look at the drop test comparison. http://www.brenthaven.com/core-protection-levels.html I carry mine back and forth to work every day, tossing it in my car (well, not tossing it, but not handling it gingerly), slinging it over my shoulder, etc. and it seems to do well.

There are numerous other choices of bags that fit well, though. This is just one example of a line that has more than just foam padding and is sized exactly for your MacBook. It can be had for less than the list price at some vendors with some poking around. Tom Bihn, mentioned just above, is also supposed to be excellent, and they make them in Seattle.