The 5" round black mirrors from Vision View Mirror Products, Inc. look like originals and come in flat and convex styles (5" diameter - as original). After installing the convex mirror on the passenger side, I decided to use convex mirrors on both sides.

They also have larger diameter stainless and convex mirrors with the same older-style backs.

These convex mirrors, mounted with original arms and in original locations, seem to provide much safer rear views than the original mirrors and they look "period correct".