Maybe my question is stupid, but where can I find material to make them? And how?Any flexible pen mold should work, you don't need a specific mold for certain resins. Most resins will work in any type of mold, but the flexible ones are easier to use. I haven't done much casting lately, but I always made my own molds out of silicone. It was a bit messy to do, but it was the cheapest way to go.