Etsy also sells a wide variety. A former provider in Louisville, “Casey Jones”, also makes them and sells on Etsy. A young provider based in LA, Kaeden, has a whole line of them for sale, which he makes.
https://kalaqtic.com/ I‘ve also been with both.
I’m a huge aficionado of them. Lastly, Gear, in Palm Springs, carries a nice line of bull harnesses. I bought a nice one at the 2019 PS meetup.