These should be SO easy to reproduce! They are thin & not too deeply contoured.
Pretty sure the heat shields were made of double-reduced, soft temper, 0.015" tin mill black, "black" meaning un-plated cold rolled steel sheet in coil. 0.015" is too thin for a cold rolled mill, so it's made on a tin mill.
0.015" is so much reduction that work hardening comes into play, and it has to be double-reduced or rolled/annealed, then rolled/annealed again.
Each finished piece weighs about 4 ounces. A minimum material purchase will be a 5- or 10-ton coil, which would make at least 30,000 heat shields if you figure 3 per pound, counting scrap. There's probably no other use for that material.
Only one thing to do: Take a chance to make a profit by selling a few hundred (?) finished pieces for $100+ each and throw a bunch of material away.
Or don't buy any material, don't make any.