This is the mica I I’ve been using. As far as the mold goes, they can be quite expensive. I started using a silicone glue tray ($2.25) from woodcraft. Packing it with three pine cone hearts the length of the tray and then pouring the resin in. They’re a bit flimsy on the sides, but I remedied that with a wrap of tape down the middle to keep it from spreading.
I was able to get 3 blanks out of each pour with this.
I’m going to be trying to make my own mold in the next day or two. I’ll try to document it and see how it turns out.