On this parts fiche the Nut is the most specified component.
A sample from the products for the Cowling(3/3)(upper) include: Bolt-flanged,6x12, Bolt-flanged,6x10, Bolt-ws,6x16, Nut,pop,6mm,l=16.5.
The Bolt-flanged,6x10 is the lowest priced item on this Cowling(3/3)(upper) schematic.