Hmmmm.................?

We need to know the diameter of the beads that the ball floats on. I would guess .177 or .22 inch..........like airgun/BB pellets.

I would take one of the balls to my local huntin, fishin, and shootin suppliers......they should be able to tell you the gauge of shotgun pellet or fishing weight?

Do you know anyone with a pair of external diameter calipers?..........they look a bit like a monkey wrench, and measure rather than manipulate.

Otherwise craft shops or ladies haberdashers........you are looking for beads of the same diameter..........it doesn't matter about the hole

Toyshops sell softair BB sized plastic pellets........... or you can usually find them on the sidewalk?.........saves having to mug a local kid?

Somehow I don't think that Kensington had the beads made to a custom size???

Good luck!