There are pop-rivets which came by OPEL.
The moldings of the old Admiral, Kapitän and Diplomat are fixed like that ones on the mustangs
I get them from the dealer shop here in my area, but the problem is they are made of aluminium.
By installing them, they disform a little bit and further they are to soft, so if you try to push on the clip the get broken
... so I will now use the repro ones with the phillips screw ....
Yours
Matthias