I’ve purchased resin ones from Accurate-Armour. They’re fine, but as they’re solid, it’s hard to add damage to them. Plastic ones may be a little better - heat and dent - but nothing beats homemade, especially when you need hundreds. Hollow casting allows for a lot of variation:
Wood works well too if you have a belt sander. Again, you can shape them individually, and really crank them out. Like reloading, once you get a system going it’s hard to stop.