If you have really deep pockets, the BMW mirrors are very nice. I couldn't justify the asking price while I was replacing a ratty pair of bar end mirrors on my 1981 R65.
I purchased a pair of EMGO rectangular mirrors that have an all-black finish. These are economical mirrors. I added small, circular convex mirrors in the bottom corners to provide a helpful wide-angle view.
Local bike shops usually stock them. IIRC, I bought mine mail order from JC Whitney. When I bought my second R65, I didn't hesitate in adding the same mirrors to the '83 model.

Best photo I could find showing the mirrors...