Beth, give these people a try. I've been to their store and they seem to be pretty willing to work with people. If they don't have what you're looking for, they might be able to order it for you. They're called Art Cast, here's their website:
www.statuepeople.com
They don't have their plaster casts on the website yet, but they had a pretty good selection in the store. Their phone number is on the website and you can call them to ask about the one you're looking for.
The store is near Minneapolis.