You can probably order some from an industrial supply catalog. I've used McMaster-Carr for most of my hardware. You might want to use Class 10.9 (metric equivalent for Grade 8) or better bolts and nuts.
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.