First, did you check the socket for power using a voltmeter?
I believe ours are fairly generic for Italian cars of that era.
I believe ours had an orange lighted ring around the socket, and I've seen green versions.
Try a vendor or eBay Italy.
Larry
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.