You might try these guys
http://www.kennedyeng.com/
They will cast you one for $350. I just had them make me one with the inverted bolt pattern for my GT40.
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.