I sourced both the horn handle and Manchurian/High Mountain Badger (26mm) online. Just glued the knot in and will see how it performs tomorrow.
I got it online through some crazy Chinese company. After a month, I emailed them to ask what's up, and they just gave me the run around. I then told them I was buying a sample to decide if I wanted to place a 500 piece order. All of a sudden, they were paying attention to me.
It is officially 26mm at the plug with 67mm loft. It is about 30mm wide where it comes out of the handle, with the remaining loft being about 54mm. So, the knot is set in the handle 13mm. I wasn't expecting it to be so big but, it feels good in my hand and I'm nevertheless pleased. In comparison, my Simpson Chubby 2 is advertised as a 27mm but, is over 29 mm at the handle. And I love my Simpson!