I'm planning on popping those mirror covers off and painting them with retroreflective paint. Problem is, all the reviews I see of the retroreflective paints say they're pretty weak, they don't reflect much.
So, if I can't find any paint that'd work, I'll get the Grade 9 retroreflective tape (you have to use amber color for the front of the bike, and red for the back, by CA law) and apply it there.
One thing I learned, DO NOT use SOLAS tape as your reflective tape... it reflects light *and* radar... making you a more easily picked-out target for police radar. As it is, the cops can't pick up our tiny bike very well (nor can the speed signs that show how fast you're going and flash blue and red lights if you're going too fast), which has saved me a few times.
"Sir, do you have any idea how fast you were going?"
"How fast do *you* say I was going?"
"Ah, well, um, pretty fast."
"No radar hit, huh."
"Just try to slow it down, sir."
"Can do, Occifer."