I need a new input jack nut - are they a standard size?

Somehow or another - I won't burden y'all with my suspicions - the nut on the input jack of my old Crate BX-50 bass amp got spun off.

Are these all a standard size? If I could just go pick one up at a local hardware store instead of going to a music store or ordering it online that would be great. I really don't care if the color matches. I just want to prevent the jack from being pushed in. If these are standard, does anybody know the size and thread count?

Thanks...