You won't be able to buy 'new' starters, but reconditioned one are the normal way of doing it. The problem is that increasingly these starters are getting ancient and really reliable rebuilds (even by Bosch factory themselves) are getting less and less frequent. It makes more sense now to upgrade to a competition type gear reduction starter motor for maximised reliability and also improved performance and weight saving, even on a standard road car.
only 2000cc has 9T starter, all others have 8T. You get the same nice gear reduction 9T starter in an S4 Spider. You can also have a different Bosch pinion fitted which is 8T, I did this once in the past and it worked well, but finding the right pinion was a nightmare!
What about the flywheel tooth count issue? I have a 74 GTV that the PO installed a late model Spider starter on. I don't like the sound it makes I'm wondering if I have a missmatch. My other GTV has a started I got from Andy Kress. It sounds much better.