This one has the correct mount:
FORD MONDEO GHIA MK3 REAR VIEW MIRROR ( AUTO DIMMER TYPE ) E11 015602. Condition is "Used". Dispatched with Royal Mail 2nd Class.www.ebay.co.uk
The main problem is the change from the 'slide' fixing on the Cougar to a 'twist' fitting on the later, more abundant mirrors.
I did think it might be possible to separate the ball and socket joints at one end or other of the Cougar stalk and mate that to a newer model with a similar stalk but I thought the re-assembly of the joint could prove problematic.
It would be possible to remove the windscreen side of the slide fitting from the Cougar and replace it with an OEM twist type fitting. A word of warning though; my mirror arrived with the windscreen slider in it along with a chunk of the still attached windscreen.
This would give you access to all the newer types and the covers for the stalk which also house the rain sensors, front view cameras etc but not necessarily the mirror wiring and connector. Having just recently helped my youngest to retro fit an auto-dimming mirror to his 2018 Fiesta we had to utilise the power feed to the interior lamps as the mirror wiring wasn't present.
I noticed 3 or 4 Mondeo Mk3 mirrors on eBay which would be suitable. Although the plugs are missing it would be easy enough to insulate a couple of suitable female connectors apart from each other and push them on to the relevant pins in the back of the mirror. You only require a power and earth unless you want to add the reverse gear interlock.
View attachment 18506
There are several OEM 'slide fit' mirrors complete with connectors on US eBay; examples:
The twist-fit mount on later MK3 Mondeos is IMO inferior to the slide-on; my kids' mum briefly had such a car and the mirror was at best insecure; I struggled just to reattach it.
Be aware of sensor aim on LHD mirrors compared to RHD. If you angle the mirror to suit a RHD view, the sensor will no longer point out the back window, instead it'll point towards the driver. I don't know if that will have an adverse effect on operation.
When I had a LHD car with auto-dipping headlights, the sensor to detect oncoming cars' lights had a slight aim to the left, and thus didn't always react promptly to cars passing on the right. It wasn't an easy thing to correct.
You only require a power and earth unless you want to add the reverse gear interlock.