PC World has an article about an iPad case that looks like an aluminum clipboard and is cushioned to protect the contents. It protects and hides the iPad, and goes for $50.
Considering how many of the aluminum clipboards I see, it would sure hide the iPad from sight. As to protection, it depends on the cushioning. Without seeing one in person, I would not hazzard a guess as to grit protection.
This is where InvisibleShield would come in handy. Lifetime replacement guarantee. Not sure if they'd honor a weekly warrant claim though, LOL.
Hard Case for iPad Protects and Conceals [The Hard Case for iPad Looks Just Like an Ordinary Construction Clipboard] TFTS – Technology, Gadgets & Curiosities