Welcome to MobileRead, Cocytus!
I'm not sure there
is a device that meets those criteria at present. I'd suggest that you take a look at the iRex Digital Reader (DR1000 series). It probably comes the closest at present, but it still has a bit to go, most notably in the battery life department. It's a new enough device that they don't have the power saving features implemented on it just yet.
There's a
forum here dedicated to it, so that's probably a good place to start.
I should probably also point out that there are rumors of other devices in the works that would fall somewhere near what you're looking for, so if you wait a half-year or so, you may find you have some more options.
Hope that helps.