Ive had good luck with the ones Ive had rebuilt locally, I have also taken them all apart to recondition myself. i have a lathe to turn the commutator or make new slip rings but the slip rings are cheap.

if you do not have a lathe but do have some sort of upright drill press you can suffice by clamping it in the chuck, and use a bearing or similar clamped tot hedrill press table, to support the other end, then you can spin it and hold a file or sandpaper against the slip rings to resurface them.

If I get the bearings and the regulator/ brush Assy locally I can save a little but to many I'd just suggest trying to resurface the slip rings and beyond that let the alternator shop do what they do best.
i do the same with a lot of tools that I need to repair for my job, saws , routers pipe threaders etc lots of tools have brush motors, not too different. same process.

I believe my new to me Porsche 944 has the same brush assy, at least I can say , I found some references that say its the same part. I think the bosche alternator Porsche used was a specific bosche one.

I believe this same brush holder/ regulator was used in other cars.
example :
https://944online.com/voltage-regulator.html