Are you sure it is the port itself? This ends up being the actual problem in around 1% of cases. It is usually an IC (CIA chip) which is surface mount on the A1200.
The guy I originally got the board off told me it had a faulty mouse port on the little board that plugs into the side of the motherboard and so I just thought I'd replace it with the pc style mouse port but then discovered that there where no pins to plug the pc port into