The Screw,flat,5x12 is the lowest priced item on this Swingarm/chain Case schematic.
A sample from the products for the Swingarm/chain Case include: Arm Set,swing, Shaft,brk Torque, Circlip In 37mm, Arm B,brk Torque.
In this schematic the "Dust Seal,13x18x3" is used most often.