I am not certain if the S1 and S2 are the same in this respect but I did get a clue during one service.
I believe that late S1 moved to several elements of the S2 including wheels/5-bolt axles.
I took the S2 into the local franchised BMW dealer to do an oil change and general fluids check over just before COVID. I highlighted the ping ping noise from the back end that matched road speed. He said the rear drive shafts were BMW 1 Series and known for expansion of the ABS rings that were mounted around the axle. This caused them to just clip the sensor. You can either swap the drive shaft or replace the rings, cost of labour made them pretty much the same unless you paid full BMW parts prices!
So from this I am going to assume that if they are the same track etc then you can definitely still get the parts. f you go down that path I would spend a little time and money doing a full check with someone like SimonH who is not so far from you. Depending on your location you are welcome to come and inspect the grubby bits of the S2.
It might also be worth changing the rose joints at the same time as the boots perish (as mine have) and the joints then wear leading to a loose back end, also an Mot fail if they are too loose. I got a warning but can feel the back end is not as tight as it used to be.
Post pictures when you do get one, its not real unless we can see it.
