FIREDOG53

Owner's manual? It should tell you what is required for the generator. I doubt that thread tape is required or should be used. You might try replacing both the plug and the gasket with the correct part numbers. I probably wouldn't use Permatex on the threads either. Are you sure that the leak is from the threaded area and not the receiver you mentioned that "moves back and forth"? Other than that, maybe a shop in the area that handles that brand...