Best way to get stripped nut off.

Ok thanks to the diagram I know exactly what it is. It is the Shaft that goes into the cross member. Is there a place to buy a new one or would it be best to just get one from another car? Sorry for the ignorance this is my first car with Torsion bars so I don't know much about them still. Also the shaft doesn't spin at all, but my passenger side does spin spin and spin so it needs a bushing if I read the posts right.