See here:
http://www.r3-forums.com/forum/289-yamaha-r3-general-discussion/7185-r6-throttle-tube-fits.html
And go to post #33 in this thread for REV2 throttle kit. Mostly for racing but you might like it. You can tailor it to your liking. About $164.
http://www.r3-forums.com/forum/753-yamaha-r3-garage-build-area/6737-track-bike-build-thread.html