My rear view mirror has similar problems. It appears to me that the rear view mirror from an Acura Legend of the same year range as the NSX would be a direct fit. The mounting shaft appears similar, at least visually, although I have not seen one up close, but have only looked at pictures of rear view mirrors for sale on Ebay. I actually bought one off Ebay a coupla years ago to try but the kid never sent it to me, and kept my money. It was pretty cheap, like $12 for mirror and shipping. I actually "caught up" with the same kid online on AOL, and gave him some heat about it. He acted real nervous and apologetic, like he was 13 years old or something.
I had been driving a new Acura TSX as a loaner recently. It had the automatic dimming mirror, which I found very annoying. It wouldn't dim enough. A Thunderbird I drove a few years ago had an automatic dimming mirror that seemed to dim more. I would rather just flip up the mirror manually.
Anyone ever try to replace just the body of the mirror and not the shaft?
ie, attach a replacement mirror body to the existing shaft.