This is a short description of how I made little doorknobs for my first miniature cupboard.
I took a little black plastic bead and a thin wire I had at home. I am not sure what kind it was- maybe steel? Quite easy to bend.
I formed a little ring using a barbecue stick and cut it off with pliers.
Then, I put the bead on a ring.
I painted it with black acrilic paint and transparent varnish. Probably black varnish would be better for this.
I glued them to the door with an epoxy glue. Ready!