Armor for Custom Mob Models

Hello!

I would like to know... How can I create an Armor for Custom Mob Models?

I'm making a model of a Modded Entity on Blockbench but i want to know how i can make a armor for the Modded Entity what i made.
e.g: I want to make an armor design for an Illager like the one from CQR Mod
Like this:

If anyone knows... Comment me!