If you're somewhat crafty, you can make a pretty decent cover yourself and choose your own fabric - I happen to like corduroy for slip resistance - and layer the fabric over a piece of wood or fabric.
Photos of the less well-done case I made here:
There's a very low profile snap-on cover available as well from an outfit called Empire.
I picked up a few of these, and went back to my homemade cases because I like the simplicity of the flip open / flip closed that a cloth hinge gives, but at 5 bucks they're worth considering.
I am not crafty so will buying a cover.
I looked at that Empire snap-on cover you linked to and it did not look like it covered the screen, just wrapped around the back.
Ideally I'm looking for something equivalent to the Apple iPad smart cover, which just protects the screen and is almost completely non obtrusive when folded back.
I purchased a very nice leather cover from oberondesign.com. I carry my NST/G in my purse every day and the leather cover doesn't add that much bulk to it. These leather covers are very nice and come in several different designs and colors and they provide very good protection not only to the screen but to the entire device. Check their website - http://oberondesign.com/e-reader-covers/nook.html - they have videos that show more detail on the covers.