At one time, DiMarzio was stocking replacements. *But, now they just say that the can get them, but they are a special order. *Should be about $100/ea or so. *You can get their contact info at
www.dimarzio.com.
The best bet though would be to just get a new set to keep in case you decide to sell, but keep the ones that are in there now for playing-the chrome will just rub off again.
Best of luck!
Chris