FP Plus is a badge that increases the max FP by 5. The badge is essentially trading a level of BP for FP, and thus it is not more efficient to use than just level up FP. This badge costs 150 coins. One of these badges can be found in the Boggly Woods, near The Great Tree. They can also be purchased from the Pianta Parlor. One is also obtainable in Rogueport Sewers, in the room with the warp pipes to Keyhaul Key and Poshley Heights.
In Paper Mario