Heinz have you contacted the MG owners club in Swavesey Cambridgeshire uk.
They do replacement rear axles & have in the past replaced parts. If you ask them they may have various sizes.
I had an axle changed on a MGBGT quite a few years back. It was a re-conditioned one. Their spares number is +441954230928 but might be worth talking to the workshop manager. Just a thought it may give you a pointer on sourcing an axle in Germany.
Good luck as the ratio change on mine transformed the drivability of my car.
Last edited by IcePack; 05/08/24 06:48 AM.