Good luck with the R4 search, where in Turkey are you located? There must be a few R4s remaining in villages in Nothern Greece, close to Istanbul etc, but they will be hard to spot...
As Malcolm said, former Yugoslavia countries would be a far better place to search.
There was a rumour that the Renault plant in Turkey was still making some sheet metal parts like floorpans wings etc a few years ago, have you heard anything?