Do you have a picture? To make sure any part I find matches..
I will be going up on Saturday so will look then
sorry no. I did not take one and it is back together with broken piece inside. The piece in question is a small white moulded nylon widget no more than 15mm wide. As I said it is unlikely to be separated from the overall mechanism whic any case springs apart when the 4 screws are undone. The unit will look like your 8v unit. I guess I would prefer a complete working unit…..