IIRC, it's a 3/4. that is slightly (.050) larger than a 19mm so maybe you could use a metric tap and die set that had a 19mm and use a 19mm nut. I'm not a professional, just Youtube certified, so I'm just trying to help you figure out options. Also, if the outer threads are good, do you have enough room to run a second nut behind the first one or add a couple of washers in front of the first nut to stay on the good threads?