If you want to be "that person" in your office, Unicomp makes buckling spring Model M keyboards, and they have one model with a trackpoint (the Endurapro). Looks like it's out of stock until sometime next year due to tooling issues though.
I used to have one of the old thinkpad external keyboards - http://www.notebookreview.com/notebookreview/lenovo-thinkpad... - and I used those until they broke and I couldn't find more.
I haven't used the unicomp ones, but I can wholeheartedly recommend the shinobi.