I'm a new n800 owner- still waiting for it to come actually and was searching for an aluminum case as well- I see that someone uses a modified Sony PSP case- so I bought on on ebay for $3. I also found this one that looks interesting...

http://pdaden.com/shop/cart.php?targ...ategory_id=491

I might try it out if the ebay model doesn't totally fit the bill.