If you capture five of EVERY monster, the arena master will give you 99 of them, you can win them in blitzball(one at a time), every omnster in the monster arena will drop them (rarely), you can bribe them from the land worm in sin for 1600000
Since Ribbon is not available on the american version of the game, I do not have direct experience with Ribbon. From what I understand the closest I can come to it is: armor with Berserkproof, Confuseproof, Stoneproof, and Auto Med.
From what I understand, Ribbon blocks all status effects. Hope that helps. Gerb has the international version, and can prob tel lyou from direct experience.