I know there have been lots of threads on the horn topic and I have read every one I have found. I came up with this solution:
They were from Banggood.com (1 x Universal 130dB Motorcycle Boat Hi/Lo Replacement Loud Snail Air Horn
(955096) US$14.49). I measured their decibel level at just over 120 at the front of the front tire. They definitely sound a whole lot better than the stock horn and cost a lot less than most other options I considered.
I have not ridden with them yet and with our temps predicted in the 20's through this week will probably not have an opportunity for a little while. Road report to follow. Now to get that Break Away throttle lock figured out (yes, I have an idea).
Did you add a relay? I upgraded the stock horn on my TBS using the factory wiring and it got louder, but only worked when the engine was running. After I added a relay to the same horn, it got louder still, and didn't need the engine running.