I think they are too small.
Maybe one of these?
http://www.amazon.com/Micro-Innovati.../dp/B00004W40X

Nah, doesn't float my boat :-}

Sadly, I can't find a picture of it on google (!) - it pre-dated the
Trackman models, not sure what year I bought it, but it was from Escom
before they went bust - it was a Logitech Pilot Trackball (and
described in the only mention I can find of note that it "looks like a
fried egg gone wrong" circa 1997)