I read on another forum that you can drill two small holes in the rear of the housing, drain out the old oil, flush with brake/carb cleaner, refill with a light clock oil and have it work quietly again.
You can reseal the holes with solder after a thorough airing out and an oil refill.
New rotors are available from a clock repair company I use called "Timesavers", they are cheap ($10 or $15) but only a couple of types are available.
Here is a link:
http://www.timesavers.com/findbydesc...ProdDesc=rotor