I pulled a real bonehead stunt and lost one of the nuts to my limb bolts on the way back from the woods yesterday. After going to the local dealer that sells Martin Jaguars and being told he doesn't carry parts because "No one really ever loses those." (thanks, dude. I didn't feel stupid enough
) I made a frantic trip to my local hardware store. After digging around with a friendly store employee, found a 5/16-18 thread 3/4" cross dowel - its basically the same part as your nut, but it's stainless and costs about $1.50. Rushed home, put the bow together - limbs are as snug as ever. I haven't shot it yet, but I really can't see a difference in the limbs.
So, if you have a big brain fart like some poor souls sometimes do, try this out.
Good luck & good hunting.