Not only on our own Fiat 850 there were problems with the wiper mechanism, also elsewhere in the Netherlands a number of small parts were missing when work on the wiper mechanism was started. We solved it by making a hybrid system of two mechanisms. And because not everyone has the parts books, I publish here the chapter Tergicristallo from the parts manual. This way we have a reference to search with.

Marelli Site

I've compared the 1968 and 1971 parts books and the only difference is that there was some extra development done by Marelli in 1971 making 4 extra part numbers available. See the table below

Parts number  1968  1971 
4110063 X X
4129427 X X
4132075 X X
4136248 X X
4101949   X
4180927   X
4184620   X
4222118   X

Fingers crossed that someone still has something lying around.