The most common minis, the pink and green go for $20. The rarer colorations can go for much more. Finding them is difficult, you'll see them advertised occasionally on some of the forums. If you belong to a local club, try there first.
I have always kept clowns with mine and they have never even attempted to host. I have a pair of ocellaris in my mini tank and they choose host a colony of palays. They have quite a powerful sting, maybe off putting to the clowns. Some of mine get rather large for minis, over 3" across before splitting, don't think it's the size that turns clowns off, especially when there is a colony of say 20tightly packed together, it's like one huge anemone.