I don't mean a separate cover, but one that was specifically designed for it.
And I think there should be one because the Kindle can't handle being put in a bag without being damaged. I'm trying to think of a device that was designed without a cover AND was designed to be portable that has such a fragile screen. If the screen is open, then it kind of implies that it can handle being used without a cover. Scratched, sure, but the device shouldn't break because of it.