There are also skins like these Nokeys
http://www.amazon.com/Protective-Sti...rds=nokey+skin
They basically have no cutout for the keyboard, but printed on letters. I can't personally vouch for those. They come in lots of designs.
I had the same crack on my K3 that appeared about a few months into owning it. I got mine when it came out in 2010 August and its still going strong, even with the crack. It just bothered me because my eye kept going to it. I put a decal girl skin on it in matte black wood and its been on ever since and I have no issues with it. The K3 is still going strong, but I am using my Paperwhite more now.
As long as I can't see the crack I don't care I guess. Out of sight, out of mind.
Thankfully my keyboard never faded.