So what is the actual part that is damaged? The hexagonal 15/16" sized nut or the threads of it? Or the pan could be damaged too when guys fail to counterhold the large nut on the pan, and the soft metal there just cracks rendering the pan useless.
I can help supply either parts, PS before you go changing the rear crankshaft seal, do be sure to replace all of the breather system parts on the engine as they can be partially or fully blocked causing oil leaks