I want to make a small figurine (about 6 cm / 2 inches high) of a Kodama from the movie Princess Mononoke. They are tree spirits, have a vaguely humanoid body and an oddly shaped head that rattles when rotated. The head is roughly as big as the rest of the body, so it would be 3 cm / 1 inch in my figurine. Here's a short clip showing their appearance and their rattling.
I plan to either 3D print the head as a hollow object or use a small plastic container that I can deform with a lighter. I want to mount the head on a spring scavanged from the tip of a ball pen. But I don't know how I can make it rattle. I was thinking about putting a bead or small marble into the head cavity, but you need to shake the head a lot more than the typical movement shown in the movie to make it rattle. Small beads also wouldn't produce a remotely similar sound to that in the movie.
Does anyone have an idea how to make a Kodama head rattle?