If the dremel drive doesn't work out, you could probably make your own version using the bevel gears at ServoCity and some Actobotics parts, like what is shown at the bottom of
this link. So far, we're quite happy with the 1/4" axles of the Actobotics set: they're much stronger than the Tetrix axles and the bearings for the Actobotics axles seem much nicer than the bronze bushings used in the Tetrix set.