Defeat the following pirate groups that appear in the Item World to get these parts. About the Commando Pirates: On the first set of floors, take either gate on Floor 5 and then the other gate on Floor 10 (Item gate on floor 5, Innocent gate on floor 10). Then, go down either route as normal.

Part	How to unlock
Black Drill	Construction Pirates on floors 31+.
Eryngi (Body)	Artist Pirates on floors 71+ (Item Growth Path only).
Galleon III (Body)	Sorry Pirates on floors 41+ [First 5 floors only (x1-x5)].
Giant Turtle (Body)	Fisherman Pirates on floors 1+.
Hunk House (Top)	Warrior Pirates on floors 61+.
Metal Aft Propellor (Head)	Red Pirates on floors 81+ (Item Growth Path only).
Mini-Yoshitsuna (Body)	Robo Pirates or Masked Pirates while Reverse Pirating (Turn 2 only).
No.6 Locomotive (Body)	Item Express Pirates on floors 41+ (Innocent Boost Path only) (Do not appear on Turn 2).
Old Wagon (Body)	Food Stand Pirates on floors 11+.
P Flonzor X (Body)	Meowkins Pirates on floors 26+.
Prinny (Body)	Prinny Pirates on floors 71+ (Innocent Boost Path only) (Do not appear on Turn 2).
Sharkpedo (Right)	Duck Pirates on floors 21+ (Do not appear on Turn 2).
Skull: Gentle Ram (Head)	Queen Pirates on floors 81+.
Starship Body G	Mech Pirates on floors 61+ (Do not appear on Turn 2).
Starship Stern G (Rear)	Rotten Golem Pirates on floors 51+.
Torn-Up Mast	Ghost Pirates on floors 31+.
Training Wing (Left)	Commando Pirates on floors 51+ (Item Growth or Innocent Boost Paths only).
Treasure Ship (Body)	Peachboy Pirates on floors 51+ (Treasure Path only) (Do not appear on Turn 2).