Used TRD quick shifter and MTEC shift springs for sale, with a bottle of red loctite included (there is plenty left, as the install uses a tiny amount).
The TRD kit shortens the throws, while providing an even more direct shifting feel. This is further enhanced with the MTEC shift springs.
This combination has gotten rave reviews from members on the forum. A buddy of mine compared it favourably to the S2000 shifter when he tried it on my car (I've never had the pleasure of driving the S2000, so I can't comment).
Costs at least $310 to get everything new (before taxes and shipping), but I'm asking $260.
For more information/user reviews:
http://www.ft86club.com/forums/showthread.php?t=77306
http://www.ft86club.com/forums/showthread.php?t=68866
http://www.ft86club.com/forums/showthread.php?t=58951