Oh God, There's a Pit in My Ball!

[AhhChoo]

Not long ago, I acquired a Logitech Marble Mouse which I've become rather fond of. If I'm a bit too cavalier when picking it up or putting it down, the track ball sometimes falls out, rolling under the couch or bed, a minor annoyance.
The ball, recently, got a tiny pit in its otherwise smooth, pristine surface, and now catches, slightly, when the pit meets one of the three contact points in the mouse's ball socket.
What might I use to fill in the pit and return the ball to its previous state of smooth perfection?
I know, I know, this is hardly an earth shaking issue, but it's enough to make me grind my teeth whenever the trackball catches.
Suggestions will be most gratefully received.