I bought my breastplate from a small shop called Transcending Effects. They specialize in custom made forms and plates. I’ve met the guy that owns the company (it’s local). He used to work for the company that made RealBreast, which is no longer in production. Like RealBreast, Transcending Effects has the most realistic forms and plates I’ve ever seen.
Be forewarned – this is definitely a splurge purchase. Several hundred at least and considerably more for lots of customization. There are plenty of less realistic (and less expensive) products that are still quite good.
3rd party URL’s aren’t allowed in the forums. DM me if you want their website. It’s also pretty easy to find with a little searching.