In general, I think tovare probably has the right idea with the Pixel Qi devices coming, but since we have yet to see any make it to market, you can still look at existing products.
You might look at existing dual-mode devices such as the Spring Design Alex, or the Entourage Edge. The Edge is aimed at students but sounds like a good fit for your needs, though it is not small, and size seemed to be one of your concerns. There is even an existing discussion about using it with external keyboards:
http://www.entourageedge.com/forums/...d-for-the-eDGe
Good luck in the search,
The Bandit