i'm in your conscience
Usually the man on the top half of Lilycove where you can jump down ledges to get to the house with the Rest TM will give you one. "A berry suits you to a t! Why should that be so?" If that doesn't work, you can fish around Pacfidlog til you find a Corsola so that way it can be in your word box.
As for the Metagross, I see no problem with Psychic, but if I'm not mistaken, Metagross is more of a physical attacker than special.