These were custom made. Not many ever got sold. They're straight-cut gears (not helical).

See here:

http://www.teamrip.com/5th%20gear.html

Good luck finding a set. I bought mine from another member on here a number of years ago and I know of no one else that has or has ever even seen a set.

Doesn't just drop in like the Evo 5th, though, as it requires a little machining/clearancing.