my starter got completely stuck 2 months ago after 220000km and 29 years. There was not too much choices. There were 2 suppliers who you can get exchange parts. Conti and Bosch. I choosed Bosch part which was reworked in the Ukraine.
Third option was to rework your own starter by a company near Stuttgart. This I did not do because of the worse condition of my own part...
I guess you have to take what you can purchase at the moment.
wish you good luck