Daily Steals is having a sale today on an one size fits all waterproof case. It was originally selling for $40, but today only it is marked down to only $2.99. You get a choice of 1 of 2 cases, either a cellphone-sized case or a netbook-sized case. Both are new and as you can see, the larger case fits the Nook quite well.
You can get most of the value from a ziploc bag, but I have to say that I like the strap. I don’t have to worry about dropping the eReader if I lose my footing.