The dimming mirror is one of the thinge we will miss from our R51 which we are just about to trade. It dims just as the following lights are getting annoying and goes pretty dark. I am not all that concerned about loosing it myself by the OH loves it.
They are omigod expensive (Best part of $1000 last time I checked) from Nissan AU for the R51, but if we could get a part number it might be possible to get one a lot cheaper from the likes of courtesyparts in the states. I just bought a pair of rear door handles for the R51 from there (Bad design on the R51 rear door handles and typical that one would break just as we are about to sell it) Around $150 each in Australia for plastic ones unpainted. $12.50 or so each from the states, painted and in die cast aluminium! Cost for both sides including freight was about $75 all up.