I bought this nice chip-on-board (COB) $12 bike light on eBay early last year. It has a white center light and red and blue surrounding the white center. I was intrigued by the fact that it runs off a 1200 mAh 18650 li-ion battery (not removable). I disabled the blue light portion of the light (illegal in NV) and used the red flashing light as a bright taillight. It has a decent mount instead of that wretched o-ring mount that you get on even some of the expensive lights. It's available in both a square and rectangular design.

$11.67 postpaid https://www.ebay.com/itm/20w-COB-LED...IAAOSw8Wdbg2VB

$11.99 postpaid for the square version https://www.ebay.com/itm/Super-Brigh...js:rk:125:pf:0