There is a great website that has a ton of information on chocolate fountains its called the chocolateguy.com. Partytime is correct you can use candy melts that you can buy at most craft store or cake or candy making store. You can use any kind of melted chocolate the best has 33% to 44% cocoa butter in it.
Exclusive chocolates or chocolate barns are suppliers of good quail chocolate to commercial fountain operators Who also supply the public !! you can buy small bays of 900g for £ 6.99 for there web sites