MOT on Friday, and I've just sheared the thread off the ball joint on the rear upper arm..

The bloody thing is rusted in tight so I cant get it out - gonna have to find a replacement...
So...
Does anyone have a passenger side rear upper control arm with the ball joint for a 4th gen in reasonable nick?
I'm told that a 5th gen would fit too..
Appreciate any help on this chaps!
Cheers
Doug