unavailable new now?
Two things of interest.
I recently (last 6 mo0nths) bought a replacement knob. Just as when I bought the original complete set they like to supply through their dealer network.
Which is great for your local bike business's.
Second thing is you can buy a really cheap look alike which has plastic brackets. Think it ok for a fall over in shed but not more.
Use sato for lower but Agras for the uppers. (look better).
If you put lower ones on the advice from Otto was that you should also put top ones on as the leg could become trapped in an accident.