If you use a flashlight, look for one that can be focused and has a CREE XML-T6 (1050 lumens at max) or XML-L2 LED (1198 lumens max). You can find both in pretty inexpensive flashlights that use the 18650 Li-ion battery. The “360 degree flashlight holder” shown in the link above was designed specifically for flashlights using the 18650 battery and that have a 1" (25mm) OD at the barrel where the flashlight clips in. I've used the flashlight for several years and never had it come loose. Pair the light with an NCR/Panasonic 18650, 3,400 mAh battery and you get long run times. Last time I looked the one shown below was available on eBay from a US seller for $8. I've used this exact model for several years
https://www.ebay.com/itm/222401132783 It is one of many similar priced T6 flashlights.
Why not use the flashlight that uses 14350 li-ion batteries? The reason is run-time, or how often you will need to recharge the battery. If you compare the same high quality Panasonic 18650 battery with the Panasonic 14500 battery the difference in battery capacity is 3,400 mAh compared to 850 mAh. If you use the same LED, the larger battery is going to run four times as long at the same lumen output. It pays to buy a good quality battery too. I've compared run-time for Panasonic versus Trustfire or Ultrafire batteries rated as high as “5000” mAh. The Panasonic 3,400 mAh ran the two cell bike headlight for 16 hours while the Chinese batteries lasted from two to four hours.