My parts book doesn't show the regulator as a seperate part. It only shows a complete alternator,A127-65, part Nr AMR3412 or AMR4249 depending on year.
The 200TDI pages show an A127-65, part Nr STC234. the regulator for that is RTC5670.
Best bet is to take it to an auto electric shop. There are parts that cross over as I had to buy an end case last year and found it locally in Virginia.