Thanks! and sorry for late reply; I don't own a 3d printer so I just draw the designs on the piece of paper (better the thicker one, almost like cardboard), and glue them on a base made of plastic bottle caps. Basically I just take the bottle caps and cut them with the hot knife (i believe using something like paper knife would be easier). I cover it with nail polish after i glued the designed i've drawn on the cap, and of course I put a safety pin on it with hot glue on the other side. They don't always look elegant, but I'm mostly happy from just the fact that I actually finished the project for once.

Another way I make the pins is by cutting off the bottom of a metal can (like the soda/energy drink one) and draw on it with acrylic markers (i recommend Posca markers although they're not very cheap) and cover it with nail polish/acrylic varnish/gloss. These also turn out well and they're larger than the bottle cap ones. So far I have one with the pride flag made from the can of dr. Pepper :3