You can buy it on the SNES cartridge but keep it mind it's very pricey as it is a rare out of print game.
You can also buy it on the Nintendo Wii virtual console for 800 points.
You can also buy the Playstation 1 altered version in Final Fantasy Chronicles.
You can also buy it on Gameboy Advance or PSP or even on the Nintendo DS.
You can also buy it on Android and iPad tablet or on the PC Steam.