I had this problem from the start (last thursday when I got mine); so much so that I had to make a quick sleeve...
... but in the meantime I bought an
Ortlieb one, but found the zips kinda get in the way when slipping it into my Brompton bag. I would have got a
Timbuk 2 one, but they don't fit the new MBP
🙁
I have emailed
wrappers to ask if they can make me a custom one.
There is also:
http://www.sfbags.com/products/sleevecases/sleevecases.htm
http://foofshop.com/
If anyone else has a good un then speak up!