PB 2w was mentioned, I have the 1w, it seems OK, obviously 2X the battery life,
because the wattage load is halved..
Spaninga taillights for fender mounting are good.. 2AAA batteries ..

but the B&M toplight Rack mount is nice & bright, and 2 of the LEDs face sideways
so arc of 180+ visible.. 2 AA powers it for a long time..