I bought one while I was there a couple of weeks ago. There is a shop which sells them in Magic Kingdom on main street, they're under the glass the counter. I bought mine from DTD, it was $40 for the chain (7 1/2inch) and I bought 3 charms that were around $30-$40 each. There was also a place at HS.
Sorry I can't remember the name of the shops for you, they were all set under the counter in shops which sold watches and other jewellery.
Hope that helps
Niki
p.s. the charms are gorgeous over there, I'm really hooked