The rubber rollers in fairground organ keyframes can be recovered by
a firm that restores rubber rollers in printing presses.  There are
a number of these firms around the world.  They will ask for the
diameter and hardness required.  Remember that the original rubber
has probably hardened, so don't get the covering too firm.

I'm not sure if the Melodico rollers can be recovered in this way or
not, as they are a smaller size.

Philip Jamison
Pennsylvania