PatB, there are 2 of them for sale on Ebay right now, both advertised as "correct production" radio plates. They are priced at $60 and $69. One of the ads says he has 10 available.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.