Be careful here.
A "sealed" bearing has a dust cover on it, not a water seal.
There are two types of ceramic bearings.
Most use ceramic balls and steel races......they rust right along with steel ones. They cost about 2x a high end steel bearing and they fail about as fast. I have used them in calcuttas and can't tell the difference.
Then there are full ceramic bearings, balls and races, which won't rust (I think their main use is very high rpm tools like dental drills where lubrication and heat are issues). They are very expensive (about 10-20X) the cost of lesser bearings. A set of small ones to fit a newell ran about $180 several years ago (I thought about it but chickened out). I would expect larger ones to cost quite a bit more, but am unsure if they even exist in a size to fit a VS.
Boca Bearings is a good source for this stuff.
Bearings come in different grades with 3, 5, and 7 the most common (7 is the best). In fishing applications I can't tell the difference, they all seem fine.
http://www.bocabearings.com/