Don't know if it fits or not, but everyone is happy with Stebel horns, and they're all over the ebay.
I've put the TM80 high-tone on my Agility 125 (fits under the plastics fine) and TM80 low tone on my Kawasaki,
stock wiring and fuse, a lot louder then any stock horn.
If you want to go all out, put both of these (they're actually sold in pairs with a relay to be used like this) OR
a Stebel Nautilus.