I think MS Road & Race sells it.
It would seem to me that the more effective place to make the shift movement more precise would be at the transaxle (where the damage is actually done), not at the shift selector (which is simply the first link in a long, and imprecise, chain).
The Wevo gateshift is the same thing, but it fits inside the transaxle. In my opinion, this is much smarter (and, as a bonus, cheaper).
Note: the gateshift is not the same thing as the Wevo shifter.