I bought pretty much a lifetime supply of polishing wheels and compounds from these guys several years ago and they really impressed me with their service. They also sell plating kits if you're inclined to do it yourself. Nickle is the most common plating on the older machines.
Here's the link:
http://www.caswellplating.com/buffing-polishing.html
They also have free instructions on polishing. It's not difficult to do yourself.
Rodney