electric wing mirror part

Hi All, we have recently bought an '04 freelander td4 sport premium. Lovely car! But caught the drivers wing mirror on a wheely bin the other day and bent it forwards a fair way. All popped back into place but when I got home I noticed that a circular 1.5 inch diameter disc of plastic was missing from under it. If I look through the hole I can see the wires etc. Have blanked it off with gaffer tape to stop moisture getting in but would like to find a replacement.
Does anyone know what these parts are called and / or where I might find a replacement?
Cheers

Mirror is only available as a complete item, independent suppliers sell spares for the mechanism but I don't think you will find a supplier of new casing parts.
That said, there are loads of junk mirrors available as when a new one is fitted the old one becomes spare. I sold the NS one from my wife's 2006 a few months ago as she didn't want to be without a mirror while I repaired her old one. Sold it on here for spares or repair.