At first I thought you MUST have XP embedded. But I didn't know of any HPC like devices that runs that. However, there are indeed PC like devices with XP emb, such as
http://www.coxion.fi/eng/tuotteet/surf.html
Anyway, as the above discussions went on, it seemed you might need something different. You said you might want something even smaller than the 680. Well, as far as HPCs go, it doesn't get much smaller than that. Any smaller and the keyboard would not be touch typeable.
There is one, the Samsung Nexio, which is only available in Hong Kong. But you might find it on eBay as well. It's got a smaller screen and higher resolution tho, so it might be too hard to read.
Chris is going to be mad... but another choice is a Pocket PC with a thumb keyboard. For example the Panasonic Toughbook P1
(rugged, expensive
), or an iPAQ 4350
(just add a protective case
).