I went through this for Aero sills. Early models were rubber (unavailable) and late models had aluminum (rare). I found a company with all the adjustable equipment to reproduce aluminum sills, and they do beautiful work, but refused to reproduce anything other than Duesenberg & Packard sills.
They were not interested at any number production run.
So, if you find someone not so swamped with orders that they can take in some work, please post it.