The keyboard Filark mentioned looks a lot like mine. You can see a picture of mine peeking out of the pocket of my case in the "any word on cases . . ." thread (if you follow the link to my flickr set).

It's a SolidTek ASK-3100 "Super-Mii". Dimensions listed as 222x103x16 mm. Works great. I can type quite fast on it. The only thing that takes a bit of getting used to is the single shift key (no right-hand shift key).