XPL, A17DD-L FET+1 Driver, 3D (5000K), 1x 18650 /18350 Battery (not included) (do not use NCR18650B), 1600lumens (max) (use 18650 protected power battery), IPX-8 waterproof 2 meters.
Basically copy coupon, view price history or create e-mail price alert. What is best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. We have found one coupon for this product!
Link: Banggood product page
1. ($27.27): BGOutlight10
put item in your cart and apply coupon code there after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): cmb1, AC18, BGS1B, FLSTNE, BGBFCR40, ECFKL, FMBG, AXMAS, 0e7f33, BGASTROLUX, BG14TH31, BGAST25, BGAFF10OFF, BGCuponation10, 4BLF, BGHONEY2110, BG10OFFAFF, BGwhielabel, BGflashlight, BG10OFFAFF1, BANGGOODSD, BGTorch4, BGYW84, BGtorch2, BGtorch3, BGtorch7
(these coupons are old, so probably won’t work)
Other warehouses/versions
This item is available in 2 another warehouse/versions!
1. China – Astrolux S1 1A 6500K 18650 Flashlight ($-3)
2. China – Astrolux S1 5A 4000K 18650 Flashlight ($-3)
Price history and price alert
Price history (for all/most countries) for Astrolux S1 3D 5000K 18650 Flashlight is here. The lowest price was: $17.9.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).