I would love a Model M2 SpaceSaver (M2s are flat, as opposed to the Model M and the Unicomp SpaceSaver chassis - also, they're all-plastic construction, which sounds bad, until you realize, it's lighter weight) as a laptop bag keyboard.
Any laptop bag that could hold your average 15.4" widescreen laptop could hold that keyboard easily.
Preferably with an integrated TrackPoint, and Windows keys.
(Hmm. There is always the BS Mighty Mouse, whenever it comes out.)