>>13420200I don't know much about what Amazon/ebay sellers are trustworthy, as I avoid that as much as possible.
Sunyshore is a good reliable site. It's a shop run by a student in Japan that picks up the item you want at a local Pokémon Center and then ships it. But since it ship's from Japan, that really adds to the total costs.
Avoid pokévault, that site is way overpriced and the owner knows it.
PKMNcollectors is good if you're looking for second hand plushies (that are in good condition).
Amazon.jp's Pokémon Store is good if you can find someone in Japan to be the middle man.
Same with Yahoo! Japan auctions, you'll also need a middle man.
Some plushies are also sold in America or Europe of course, but most of them are Japan exclusive sadly.