For those in the states one doesn't HAVE to approach CMV, for me they're not far away, but keep in mind that the company has changed ownership & the staff now there are not the staff who used to fab these springs 20 + years ago. The last time I spoke with the current owner John Geropolous none of the staff had any experience putting together one of these multi leaf springs to replace the glas leaf. When the original owner Alex Vitanoski & his son left they took the know how with them.
But that aside any capable spring shop can fab up a replacement for the glas leaf, all they need is the car, the old spring & do the formula to make a 2 leaf or 3 leaf replacement that will be either a high arc or shallow arc, oem height or custom height depending on what you the owner are looking for. The indepth part is getting either outboard side of the chassis mounting points exactly the same arc so the back end of the car sits even.
Because of their lack of knowledge I did not go to them, instead I used a spring shop close to home to fab what is currently under the car.