Someone here had the exact doll that was used in the film. If I recall, they ran across it in some second hand store or antique store. It needed some work, but the buyer managed to restore it.
Sorry I can't tell you more than that, and I don't think anyone on here has attempted to make a replica....yet.
Can I jsut say that reading the title of this thread was enough to give me the willies?
Found this online:
The clown wasn't available for purchase. Doll maker Annette Little made four copies of the Poltergeist clown. Three of them were made for the movie. Annette made the fourth clown for herself with MGM's permission. It was reportedly on display at her San Diego store, "Here Come The Clowns."
I friggin' HATE that clown!!! That thing was the scariest thing in the movie and shaped the way I've viewed clowns ever since... they scare the crap out of me!