I have never found those for sale unless they were used ones taken off a '66 Signet.
That trim is also held on by a few threaded butterfly type and if there's access to install the nut those could be used.
I don't think this one is wide enough but a similar item might work. http://m.ebay.com/itm/20x-Fit-Plymo...ips-NOS-448-/371419818277?nav=WATCHING_ACTIVE