It was a option and yes you can add one. If this is for your 69 I believe they reproduce them but not 100% sure.
Option depending on year . I see no problem adding a RS mirror . In fact Its a safety feature . I can't drive ANY vehicle without one .
Yes, the bracket requires drilling a hole to secure it. Guys with 68-9 cars should be able to give you precise measurements, and pictures so you don't make a mistake. https://www.opgi.com/mirrors-hardwa...r-outside-1968-69-skylarkriviera-s240653.html
The 1968-1969 Buick passenger side mirror was a dealer, not factory, option. The mirror was used on the entire Buick line. It is the same shape as the non remote driver side mirror. Jim Vesely ROA # 7437 BCA # 39477
I believe you can buy just the mounting plate from CARS. The mirrors originally came with a template for where to drill the holes. The '70 template is posted on here but never seen the '69 or '71-2 templates posted. Surely someone has them.