I found one off Ebay UK for my Mangusta from a seller called "rutwilliam_48". £100 / $125.
If I search that seller now it takes me to EverythingretroFord. They have a selection. When I spoke to them about mine it seemed they were working through their inventory, apparently they bought up the NOS of a Ford Dealer so were unsure of makes / models so you have to ask them to measure etc, but mine was unused. Maybe they now have a business site for it all.
From research I did it looks like the indicator / turn / flash and horn combo with silver end (they are also available new for a few 3 off Ebay UK) were Escort Mk1 or Capri Mk1. Mine was completely missing so I had to have the cancel ring remade and one Capri item I initially bought from someone else wasn't correct so make sure you specify the diameter you need.
The Ford parts are becoming expensive especially early Escort where the Mexicos / Twin cams fetch big money. Not Maserati or De Tomato expensive parts but getting that way. This is link to this seller (no connection but they do seem to ship International if needed)
Cheers