You should've used the J-Pop thread to ask this

But it's probably on page 3 so whatever
Anyways it's not just Amazon J-Pop is just expensive. YesAsia is the best site they pretty much will have anything your looking for.
Other alternatives are CdJapan and ebay sellers. But your most likely gonna pay a pretty penny either way just the way it is

The HongKong/Korea version thing is a must if its available.