Generator brushes

[Redbird]

I am learning as I go and decided to see if I could adjust the third brush. The ampmeter is registering almost all the way over to the right when running in the daytime. So I took the cover off and not exactly sure how to adjust. Also, while I was taking off the cover, I see that the nut is missing off the bolt that holds the generator. Does anyone have a spare or can it be picked up at the hardware store?