http://www.virtual-laser-keyboard.com/ ?
Or for something more sensible, google 'waterproof keyboards'. There's loads of rubber ones that you can roll up and do all kinds of things with, and I would imagine that its all one piece, so no removable keys.
My partner just had the solution.. Buy the keyboard.. remove all the keys yourself, and SUPERGLUE them back on again. Get those keys off again you little........