Genuine MGR towing mirrors, I tried various aftermarket types, none of which ever fitted very well. Got a set of MGR mirrors, still boxed, for around £50. Only thing is due to the age, the rubber straps were starting to perish. So I swapped them with the straps from a universal set.
Generally a set or 2 for sale in various places. There was a pair on facebook a couple of weeks ago but can't find them now. But there is this pair on eBay at the moment.
https://www.ebay.co.uk/itm/ROVER-75-...8AAOSwPL9ddl9r