If you really want to go on the cheap, find a EVA PDA/GPS/NETBOOK sleeve that has similar dimensions to the K3, shoudl be around 5-10$, or you can just get one that is designed for the k3. Beware, alot of people will mislabel netbook and other device cases for k3.
EX: k3 is 7.5" x 4.8" x 0.335"
The k2 is little bigger than the k3, so k2 sleeves should fit just fine.
I would recommend something like this:
http://www.amazon.com/gp/product/B00...ard-case-black
or
http://www.amazon.com/AMAZON-KINDLE-...3&sr=1-3-fkmr2
The case crown cases are really nice, i got one for my DX. They are low price, and the quality is surprisingly high. There are no flaws in the workmanship, the seams are good/hidden, there's no threading spilling out/etc. The zippers are padded too.
It's EVA (hard semi-flexible plastic material) on both sides so the thing won't get banged around if you put it in a bag or something. Also you won't have tons of crap on the device when you take it out to use it. Those covers are a hassle that you have to fold back. And don't get anything that covers the screen, it adds glare and looks terrible.