Wayne, Triumph in the US did offer a rather nice door mirror in the 1960s. Unfortunately, I broke the only one I had, and they are very difficult to find. Pretty typical configuration, but a bit more appropriate than the typical heavier types found on American cars. Apologies for the ancient low-res.scan here.
Meanwhile, Wayne, do keep me posted on the barn find!
Thom, I am intrigued by that interior mirror. On a TR or Spitfire, I can see how that might be nearly ideal even with the top up. On a Herald convertible with top up, there's a somewhat significant blind spot; not huge, but there. For that reason, I think I'd still want an exterior passenger mirror on a Herald convertible. No problem on a Herald sedan, though!