Answering my own question, I'm using the Matias Folding Keyboard with the eDGe and it works GREAT!

It's considerably bigger than the Targus one, but it has full-sized keys (except for HOME/INSERT/DELETE/etc) and it even has a (full sized) 10 key. The keys feel sturdy and give solid feedback for touch-typing (more so than Targus, IMHO). The only annoying thing is that it must be used on a flat surface (i.e., there's no way to lock it open if you were to use it on your lap or something), but that's my only complaint so far. Highly recommend!

EDIT: I can't seem to get the 10key to work on the eDGe (it works fine when connected to my laptop). Still a good portable keyboard, though.