Black craft foam clay.
Craft foam clay is an air drying clay that dries to a foam which is slightly spongy. It can be used for adding detail to cosplay and prop making projects.
It is a little tricky to sculpt/form/add detail when wet, so best to stick the clay to your EVA prop with water, sculpt as much as you can in-place, then leave it to dry.
You can then further shape it with a Dremel, knife, sanding paper etc. to get the detailed finish you require.
We make a 140mm version of a Celtic coin from Craft Foam Clay, craft foam and Hexflex foam sealer.
We found you have to handle the craft foam clay very carefully to ensure a smooth finish.
It dries to a spongey solid consistancy similar to EVA foam.
Sticking it to the craft foam sheet with superglue worked really well and priming it with Hexflex resulted in a robust model that would be fine for theatre prop & cosplay applications.