I lost the screw that hold the antipivot nut of an 30+ year old Raleigh Grand Prix rear derailuer (Raleigh brand on the der)-I still have the nut-i.e. the nut that goes into the dropout of an axle mount rear der to keep it from pivotting. Anyone know anything about the threading on the nut I'll need to replace it-can I use hardware theading, will it be special bike threading, metric threading, etc? If special bike threading, is it still available or will I have to pull it off another axle mount der of that era?