... I noticed this ad on eBay, they claim to be able to supply or source any Volvo parts:
https://www.ebay.co.uk/itm/Volvo-Gen...53.m1438.l2649
I have no idea whether the service is reputable, but it might be worth giving them a call to see if they have the RHD cable (although sawing a slot in a nut would be much cheaper and probably work just the same).
Good fortune,
Alan