I use a few German sites:http://autoteile-glauner.de/products-page/ersatzteile/ersatzteile-w114-w115http://mercedes-lager-teileliste.de/liste.php?baumusternr=68https://www.niemoeller.de/en/w115/w115/B110/http://oldtimer-ersatzteile24.de/Mercedes-W115
Also ask on the German site:http://www.strichacht-forum.de/
and or search their knowhow page - run through google translate. http://www.strichacht-forum.de/knowhow-v2/index.php?title=Hauptseite
I did the same as you by accident or design, picked up a LHD version partly because there are lot more LHD ones surviving.
It might be worth, if service items aren't too expensive, buying enough for 2 or 3 services to make the postage worthwhile.