I can't tell what trim cap is missing, but I have the washer http://www.fiatplus.com/washer-for-bush-4179945-pr-303973.html
Chris Obert
It's the cracked bit in the photo. It covers the nut.
Maybe he means this? But it doesn't look quite like a perfect match.
http://www.fiatplus.com/black-wiper-post-surround-pr-299814.html
I hope this clears things up.
Two steel nuts, rubber washer on the body (same as Yugo) and a trim cap. Under side of the cap fits the nut. Cap in place. This may be for a very early car or very late. You tell me.:wall: