I like your project. But for those who don't have a workshop, I wonder what an alternative material or design might be. A strip of rubber from an inner tube or bike tire, or some kind of a thin plastic sheet? A plastic container material like a milk jug, or a thin piece of wood? Or use the top from a plastic or glass jar. I've seen cappers made from thin flexible rubber that only had small round holes in it, and they hold caps well enough to be sold as a capper. Just punch a hole in thin material with a paper punch or belt punch of some sort, unless it needs to be drilled.