I just bought my nexus 10 and while waiting for delivery I went on eBay to get a book cover..
Quite a few from U.S. suppliers, Quality makes, delivery makes it a tad expensive for us down under,
Several from the U.K. quite cheap, and the usual offerings from Hong Kong and Mainland China.
I bought from the U.K. cause mail from China takes wayyyy to long and things get lost...
( an sometimes thing's arrive safely and reasonably within time.) But you never know..
So hop on EBay if its available to you, or Amazon probably have them to.
Kogan's also have nice book covers for N10, $25...
Go check them out...
Love in my N10, my old TF201 just had to be replaced...get on it