Alright definately appears to be plenty of interest so I will get myself setup to be able to do multiple door trims.
I'm leaning towards ABS plastic as I think I could do the entire thing as one piece i.e. including the normal bulge and the turnover at the top to hold the window scraper.
That means it wouldn't requiring the metal part from the top of anything else off an old door trim. Also never have to worry about it getting wet.
Backup plan, I could definately make them out of masonite and attach a bit of extra timber to recreate the bulge.