Have you tried a helmet or glasses mount mirror on the right side. Might need to be inverted to get the adjustments correct?

I have a fairly wide field of view with a left mounted glasses mirror. Enough to sweep view the right shoulder of the road without too much movement.

Lord, I feel naked without a mirror. I can't see how you do it. Depending on the bicycle type a right side bar mount may help, also. What's coming up from behind is of primary concern....you'd get that seen with a right side set-up, too, probably.