I don't think Disney sells them any more. When we were planning our June wedding (6/3/2011), I wanted the castle topper more than anything else. I was told that the only castle topper they have is made out of White Chocolate. It is actually made by Impressions by Shelley/Fairytale Wedding.
I spent several months before the big day scouring online, and nothing seemed to come close to the beautiful topper from Disney. So we broke down and bought the White Chocolate topper.
We brought it home, and I've talked to a chef who preserves food for displays. He suggested shellacing the castle. I'm looking into different ways that I can preserve the castle so I can display it, rather than leaving it in the box in the refridgerator.
I know this is not what you want to hear, but please keep us informed. I'm sure plenty of Disbrides would love the polyresin topper - I know I would buy one in a heartbeat!