Alternative GO pieces

A good friend of mine is making me a new go board out of wood. The thing is, actual go stones can be pretty expensive, and I don’t even have the money to buy any and my friend is capable of 3D printing a set anyway. But, they can’t be the same exact shape as traditional pieces. The ones he made for his own set are flat on the bottom and convex at the top, 6mm tall and an inch in diameter give or take a few mm. I felt them, and since they are 20% solid they are extremely light. I think the feel is a bit strange especially since the edges are not rounded.

Does anyone have an idea for an alternative but comfortable shape I could make?

Make a hole inside a stone put some weight inside it.