S1 Passenger Door Window Winder

[BavarderS1]

Hi everyone. I posted a query about sourcing a passenger side window regulator a while ago as mine is 'kaput'. The cable has snapped.
Lots of useful info received thank you very much but I have not had any success in sourcing the part (which are from a 1985 Audi 4000 Quattro
or 1979-1987 Audi A80, part no. 813837399D) even through the classic Audi car clubs. As people say it is like finding the proverbial hens' teeth.!!

Has anyone tried to successfully repair one of these? If so some advice about how to go about it will be appreciated.
Thanks

Tony