Greg Merritt at Hillbilly Daiku was kind enough to let me know that Japan Woodworker (JW) does indeed sell the brushes for Uzukuri. It only looked to me like they did not. The reason being that JW calls them texturing brushes, and does not use the Japanese word.
For what it’s worth, I think they appear to be over priced. Maybe after I try one that opinion will change. For now, I just can’t part with that kind of money for a brush. Perhaps I’ll never know what a joy they are to use.