Looks like it is the same rear fog light as on my Boxer.
If you're still looking there is one on Ebay now.
http://cgi.ebay.com/ebaymotors...QQrdZ1QQcmdZViewItem
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.