I got a undertail from extreme graphics that use the stock brake light. The trick about it is you flip the light upside down so the reflector is inside the tail section. It looks realy good. I would show pics but mine is currently getting painted, so any way go to this site and scroll down to about the middle of the page. It is a fiberglass undertail, I got mine off ebay for about 130 instead on the 179 on the main web site. Hope this helps
http://www.exoticsportbike.com/hayabusa_(1999-2005).htm
http://www.exoticsportbike.com/hayabusa_(1999-2005).htm