To the OP:
If you truly want to go with ceramics, check here to see if there is a kit already available:
http://www.bocabearings.com
If there's no kit, then if you can determine the dimensions of the bearing catridges, you can search their database for the correct size.
If you need loose ceramic balls, they have those too.
DISCLAIMER: I have no affiliation with BocaBearings other than being a happy customer.