I don't know if this will help you, but the green plastic was missing from my emblems.
Not knowing how they were attached, and not wanting to create a mess with a botched replacement attempt, I followed a suggestion posted to the old Alfa Digest, and painted in the green using 4 coats of Testors #1157 Green / verd hobby enamel. Cost was $ .99 plus artist brush. Not an exact match when compared to the NOS serpent I later bought, but not bad looking at all.
I applied the paint with the emblems in place on the car, so that limited how much paint I could flow on per coat. Now that I know the badges are held in place with pins, I might be tempted to remove them so they could be laid flat to allow heavier coats. I blotted clean the raised outlines using a thinner dampened rag wrapped around a flat block of wood.
This seems to be the cheap way and safe way out, as opposed to buying repros and attaching with trim cement.
The colors in the photos may be a little darker than actual.