I have to agree with Candice. If you have a small chip you might be able to get away with a small touch-up like on a car but I would leave it alone too. Especially if it is honest wear like you said. I would tend to stay away from a repainted machine. It may wind up looking like you are trying to hide something worse than chipped paint. I like to see that wear on a machine. If it is all worn off right down to bare metal you could have a valid reason but it doesn't sound that bad. I have looked and looked for reproduction decals too and there just aren't any to be had except for the Featherweight Singers.
~G~