On this parts fiche the Washer,lock is the most specified component.
Some items from this specific schematic: Washer,lock, Gasket,exhaust Pipe (nas), Plate,exhaust Pipe, Washer,lock.
The most reasonably priced component used on the T20 Tc250 Scrambler 1969 Usa (e03) Exhaust Pipe-muffler is the Washer,lock.