Assuming you are referring to Flight of Legends meaning the Japanese version of EX Fire Red Leaf Green…
Supply for sealed Japanese PCG era product is virtually nonexistent. EX series was a low point for Pokemon in general, even more so in Japan. At the time, the people who were involved with Pokemon were mostly TCG players, so the cards were opened from packs a lot. Flight of Legends is actually one of the boxes that I see pop up occasionally. Stuff like Holon Phantom, Furthest Ends of Offense and Defense, and Miracle Crystal are probably some of the hardest sealed boxes to find in the entire TCG.
I don’t think it’s so much a problem of you being late to the party, than the party never happening to begin with!