I recently added a Wolo Bad Boy air horn to the V-strom, mounting it in the upper right fairing. I used a relay triggered by the old horn contacts and powered the new horn directly from a fuse box under the seat.
The horn itself was mounted using a u-bolt around a vertical fairing support and a short piece of flat stock.
I’ve had to use it a few times and it definitely gets more attention than the wimpy stock meep-meep version! If you have some basic wiring skills, I highly recommend it.