have you considered finding wooden beads the right size and painting? you could even carve out circles to fit the eye chips or even rhinestones and such.
Those are styrofoam balls and air dry clay and idea wise it's pretty good. I wasn't getting them to be completely round so I tried 22mm wooden beads which fit better in the sockets but wouldn't line up to spin in the mechanism. A dowel would have worked better than a straw.
Ultimately I did get Freaky Frieda an eye mechanism.