Shepherd I think you will have better chances if you search your glass outside US. I am pretty sure that OEMs don`t like any bit what you are trying to build and can even pay glass manufacturers not to make you any glass...
Citycab glasses were just free formed so only heating in a oven it its frame. It took many test pieces before that rear glass got perfect shape because there was not that tooling under it. I think those had E marks needed in Europe, but the price is very expensive if they are willing to manufacture them.
Those glasses were made at Pilkington Laitila factory:
Toimipisteet
In Finland you are able to legal permit in some cases to use something that is not sertified / verified glasses. Specially if the case is good and it project has clear purpose.