Pete, it's actually chinadog who is asking the question.
With regard to the NTE TB-105 thrust bearing, I went to order one of these earlier this year, only to find they are no longer available new. I searched and searched, and eventually got hold of a well-used one. It seems like the usual story - the availability of OTA equipment grows ever smaller.
It is not difficult, however, to make a thrust bearing with a sleeve of ABS, PVC or metal piping sized to fit over the mast, and grease applied between the mast and piping. I used that approach successfully for 14 years until I decided to 'upgrade'.
For several years, I had a 91XG on a small rotator comparable to the Channel Master (the Eagle-Aspen DiSEqC rotor), with the pipe thrust bearing. I replaced the 91XG with a 'monster' CM3671 antenna. The rotor failed after a few months - due, I assumed, to the increased wind loading. I upgraded to a Hy-Gain Ham-4 rotor with the NTE TB-105 thrust bearing, and all's well so far.
I also have other three-wire rotors, and bench testing shows how quickly they get out of synchronization. Merely starting and stopping them several times in a full rotation puts them out significantly. Either the DiSEqC control (of the now-unavailable Eagle-Aspen rotor) or the potentiometer feedback of the ham rotors is necessary for accurate and repeatable pointing. Otherwise, one is obliged to run the rotor to end-of-travel each time to re-calibrate it if accurate pointing is desired.