Where can you buy a head for a ball jointed doll?

I really don't know if you can since the people who make the moulds would be selling the dolls they make, therefore they would not want you to have the moulds because you could make MANY dolls from them. If you would want a BJD you would probably have to make the parts yourself then mould them yourself but if you can't do that then you might have to just buy the dolls.