Dual Bike Mirrors
I have found after many miles of touring that dual mirrors are better than a single left hand mirror. (I don't a helmet mirror for various reasons.) When you are riding in the road and swing to the right on a curve, the right mirror naturally shows traffic approaching from the rear. After a while, using two mirrors becomes natural and you feel blind with only one mirror. People that use no mirrors are either crazy or suicidal. Note that all motorcycles have two mirrors. The only drawback is that mirrors come only as left hand mirrors. The original metal brake hood Rhode mirror, bought out by Bell, has been discontinued. It has been replaces by a much inferior plastic one that vibrates badly. The new STI brake hoods have a wider width than the aero style 'brake only' levers, and you have to check shifting clearances if using these type mirrors on STI shifter/brakes.
Because the original hood mirror still vibrated a little, I made my own using a slightly heavier gage aluminum as seen in the two photos. The result is less tendency to vibrate and at a lower frequency. I also put reflective white tape on the front and back of the mirrors. The right hand mirror is the mirror image of the left mirror. The mirror is a two piece assembly held together with pop rivets.. The mirrors themselves are old round Rhode mirrors. Sometimes you can still find the round mirrors, but rarely.