Zac Higgins has a video on making ribbon blanks, or specifically ribbons for ribbon blanks. There are a few other vids too. The only way I think you could get close to those would be to perforate your own ribbons after casting or cast the ribbons on a mold with raised bumps. A piece of glass with silicone mold making dots all over it would probably work. Don't expect a clone though, those blanks are made in an industrial setting and would be very difficult if not impossible to clone at home, but you could get a similar effect with some trial & error. This is purely speculation, but it's how I would go about it. I've made a few ribbon blanks, just not ones that had the perforations.