The 8 pin connectors for the Fiesta Mirror uses Molex shells from the 30700 series. It is possible to get a 10 pin male/female connector from the same series, that way you can depin the current connectors and re-insert them into the 10 pin shells, and have pins spare for the extra lights in the mirror. These connectors all come with a number of 'keyed' options - small slots or cuts that make the connectors unique, with part numbers in sequence, 1081, 1082, 1101, 1102 etc. This 10 pin connector for example is also used on the back of the climate control dials, but with a different key pattern.
https://www.molex.com/molex/products/part-detail/crimp_housings/0307001080
https://www.molex.com/molex/products/part-detail/crimp_housings/0309681080
https://www.molex.com/molex/products/part-detail/crimp_housings/0307001100
https://www.molex.com/molex/products/part-detail/crimp_housings/0309681100
These connectors can generally be found at places like au.mouser.com or element14. If you are adding pins, you may need to determine the wire gauge you want to use and the molex site can help get you find a part number there too. I'd guess that 18 or 20 gauge is used.
Lukeyson