9b11f552____Final_Fantasy_X_2_Item_List__Location
[Name] Machina Booster [Description] Enables Machina Maw to learn Break Damage Limit. [Location] 
At the end of Mushroom Rock Road by the Elevator that takes you to the Youth League Heardquarters during Chapter 5, there should be a chest south of the Elevator, open it to receive the Machina Booster.
Final Fantasy World - Final Fantasy X-2 Item List
Location