An3 an4 and an5 penny washers are also useful to have on hand will get you out of trouble, As well as AN (a)bolts and nuts ,Cotter pins.
The washers can be uses up to a maximum of 3 per bolt if you have to but preferably buy the appropriate lengths e.g AN3-4 and so on keeping in mind between 1 and max 3 threads should be protruding from the nut.