Gamiss offers the Wowsawe LED Bicycle Flashlight for $7.17. Coupon code "MAYNEW01" drops it to $4. With free shipping, that's $12 off list and the lowest price we could find. It features an adjustable beam and includes a swivel bracket.
Note: This item ships from China and may take two to five weeks to arrive. Also, uncheck "shipping insurance" at checkout to dodge the $1.08 fee.