Does anyone know how I can replicate the internal cotton and plastic bits from some Beyerdynamic DT770s?

[Spasticteapot]

I'm working on some custom DT770s made of wood and aluminum. (Plastic? We don't need no steenking plastic!)
 
Anywho, I have some DT770 drivers, but I'm missing the little plastic "crown" and surrounding foam. Does anyone have any tips on recreating this? I do have the driver assembly and passive radiator.