Troll and Toad offers sealed boxes of the Final Fantasy TCG.
There's also
TCGplayer which offers a very wide selection of singles and sealed product. Just check the box and narrow down your search.
I've been collecting it for awhile, mostly english cards from when they began using new original illustrations for their card artwork. The game hasn't taken off locally where I am, but I still enjoy buying and collecting certain cards. I have that promo Cloud that advertised the game when it first got its global release and managed to snag the limited edition Vincent Dirge of Cerberus deck box and promo cards from the S-E store. You might want to get it while you can because once it's gone, it's gone for good and the Advent Children Fenrir deck box is worth hundreds of dollars.