tiktox is popular with the European fans.
http://www.tiktox.com/
On eBay the popular Singaporean dealers for Seiko will also sell Casio. Just be careful if you are looking for something atomic, they most likely will not carry it because of the market. They will often have the same model just with solar function instead. Sellers that come to mind are krazy's, watches-bay, premierworld, and someone from HK named hkexporter. I have no personal experience with these dealers as there are enough US ones for me, but I have seen them recommended in the past on another forum.