I used common HVAC galvanized sheetmetal when I made my heat shields. I have a set of full-size templates, but they were copied for a CMC and you have an intermeccanica, do you not? I'm not sure if they are the same.
Regardless, I first made a paper template from heavy wrapping paper and traced it out onto the HVAC air duct metal and cut it out. The CMC has a square, horse shoe shaped frame member around the engine so I just screwed it right to that. You can use a VW bus "H" gasket between the heat shields and the engine specific tins to seal up that gap, too. Seems pretty effective for the past 20 years or so.
Hope this helps.