Truth be told, if the left handed threads are damaged, I do not know what the best way forward is. I think the rivets may have to be removed from the AAU. Such is above my pay grade, so when I needed to remove the bolt from my AAU, but could not, I purchased a second hand replacement AAU. Maybe someone smarter than me has a solution?
If you cannot find a good used one I think Norvil sells them rebuilt. You may have to provide them with yours as a core.