I used a Kindle for a week (swapped with stepbrother) to try it while he tried mine.
The Kindle is definitely too wide.
DB had a novel method of protecting his, he put it on his homeowner's insurance as a "valuable" item. He also hates the Kindle's cover but loves the page turning ease (so do I). The keyboard needs some sort of cover to hide it.
He actually glommed onto one of my pencil cases to use for his Kindle. I had been using it for my Cybook before I got the Circa case. It does not zip but it does act as an easel which is nice. The only place I know where to get one without the pencils is in Ebay (they started carrying the case without pencil after the art class I teach decided to request it en-mass). And it's only $5.99+2.99 shipping (less than $9). And it is my favorite travel brush and pencil holder too.
http://cgi.ebay.com/COLOR-PENCIL-EAS...713.m153.l1262
(this is one of the most reliable ebay sellers of art supplies I've ever used)
His final solution for his Kindle for real protection was a Steno Pad zip around folio. It's a little big, but he says He feels safe with it in his carryon bag.