You can get them from Suby Sports http://www.subysports.com/
for $250. I think Larry from imprezaRS.com may also have them, but that may be a rumor. I'd check with him at email@example.com
. It's fairly easy to install and takes about 1/2 an hour. I actually had Suby sports install it for me and they were great.
Oh and I believe it's supposed to get rid of the speed limiter, but I could only get up to 115 today (the point where it used to kick in;didn't this time), but slowed down cause my shocks are pretty badly worn out and didn't really want to risk it with the wind blowing as hard as it was from the side.