2008 Prius. Moved to a house built in 1954, single car garage, and it is NARROW. I back in, so that I am on the side with the entry door in to the house. Being able to fold those side mirrors would be a big help. I did search, and I found several folks talking about these, wishing there were some. But I couldn't find if there ARE any.
Toyota Prius 2004 ~ 2009 NHW20 Exterior Accessories :: Sigma Automotive Has “JDM Signal Mirror Housing” that has built in motor. But you could probably just get used one from Japan. You probably don’t need the “Auto-Folding Mirror Module” since you want the mirror(s) to fold while driving? But you do need to at least somehow wire in the switch to control the folding motor.
