It looks like some cases for the Blackberry Playbook might work. To compare the dimensions the Playbook is 7.6" by 5.0" by 0.4" so it is a little wider and taller, but a bit thinner (by about 3.5 mm).
I would try to find a case the uses the elastic corner tabs.
I might try one of these:
http://www.amazon.com/gp/product/B00...A34I76D6T5OLHY
http://www.amazon.com/gp/product/B00...A1QGIDACEIIO9M
http://www.amazon.com/gp/product/B00...A3JRBTF3T7J4ZI