"Steve"
I'm not sure what you mean by thrust bearing. I have a 10 year old
Windbugger that is just back from a factory overhaul. They replaced a
bunch of brushes and bearing and sent me the old ones for spares. I didn't
see anything that looked like a thrust bearing..

Thank you for the help. The thrust bearing assembly is what allows the body
of the generator to stand on top of a pole and turn freely to follow the
direction of the wind.
It is presumably made by one or two ball bearings fixed to the pole (inner
ring) and to the generator body (outer ring). Within the assembly there
must be also a way of transmitting the electrical power from a free turning
part (the generator) and a fixed part (the pole): probably by means of two
slip rings.
Assemblies like these can be adapted from surplus material but I would
appreciate advice.
The name "thrust bearing" is what the guys at Windbugger call it and
commonly stands for a particular ball bearing which supports an axial load
(as opposed to a radial load). In this case both loads could be important.