i take it you have the airship. are you aware of the small town that sells mythril armour. its called silvera. its a town full of people who have been minied so its a bit of a weird place. it is located in a long row of islands south of fabul and north of Mt.ordeals. nearly directly inbetween them. i cant remember everything that they sell but they sell the best armour at that point in the game.