This small catapult is about 5 cm x 10 cm and using 1 piece of rubberband.
It is functional, but I made it from scratch and for desktop display.
The wood I used is 0.5cm square rod.
The "pocket" is the cap from laser pointer.
The "wheel" is small chess.
The "wheel axis" is toothpick.
They are sticked together with hot glue.