If you strip it and measure them you should be able to buy the bearings from most engineering supplies places.
PG winches used to remanufacture all the obsolete parts for these overdrives and many winches but since Phils death I haven't heard of any one else bothering.
I certainly wouldn't strip one to fix the other just try to get them both going its not rocket science just simple engineering
Super winch are still trading so I would give them a call and see what they say, if they send you are drawing and you can possibly id the bearing size its very easy then