Our JD dealer has nuts and bolts by the pound. The way they advertised it when they switched over, I thought it was a JD-wide thing. Guess not!

"Here", the local Fleet Farm has bolts by the pound, big bins of grade 2 and small boxes of grade 5. Can't recall the price/lb. True Value hardware store, too.

You don't need to over-do the inventory, a half dozen of each size will get you through most repairs-if you have a project, you'll be going to town for other stuff anyway.