For $6.99 each, Autolumination makes a tiny red LED called an Eagle Eye....puts out 200 lumens, which is more than most flashlights.
Eagle Eye 3 Watt Accent Indicator Light
12 Volt
200 Lumens
Fits thru 1/4" thru hole
1/2" face nut
3/8" back nut
All Metal
Waterproof
Will flash, if used as turn signals.
Or simply wire it in with your brake lights.
3 of those, mounted near the top of your backrest....
autolumination.com/indicator.htm
This is an outfit that got a lotta BAD reviews, awhile back.
If I had been interested in reviews, that might have stopped me right there.
I have no connection with them, except as a satisfied customer.
I've ordered stuff for my bike + friends' bikes; everything has been top-notch, in 6 orders.
On two occasions, I have called them with specific questions....and got sensible, polite answers, geared to my level of understanding.
Didn't aim to write a sonnet.