You can get Convoy S21A SST40 Flashlight for $18.59 using coupon code (in Banggood). You can create price alert here, copy coupons and view price history. What is the best price?
Latest coupon code price check (UTC time):
Tailstand: Yes, LED: SST40 6500K white tint, Mode memory: yes, Reverse polarity protection: Yes, Color temperature: 6500K, Low voltage warning: Yes, Reflector: orange peel, Battery included: no, Range: 50 – 100 meters, Whether to charge: no, Number of lamp beads: 1, Lens type: Ar-coated glass lens, Whether to remember the gear: yes, Light effect color: white light, Body color: titanium gray, Is it waterproof: level 8, Voltage: input voltage 3 – 4.2V, Lumens: 2300LM (maximum), Required battery type: 21700 or 18650 lithium-ion battery (not included), Required battery quantity: 1pcs
Banggood ($18.59)
Banggood warehouse is located in China. I can’t find any active coupons for this product in Banggood. Price? From what I can see this price is higher than average price ($18.42).
Link: Banggood product page
Price: $18.59
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGS21A, BG7S21A, EYBG, BGTORCH, 502C6B, BGBFCR41, fInbG2020, BGff2020, BGCONVOYSS, BGCONV, BGflashlight, BG10OFFAFF1, BANGGOODSD, BGTorch4, 00c906, BGtorch2, BGtorch3, BG8Alerabat, BGLED07, F03081, BG5de8a6, FIN1443, BGOutlight10, BG29ddce, BG6be74d, BGBLF26, BG589b2e, BGd57765, BGHOBBY240, Fin0308
(these coupons are old, so probably won’t work)
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Here is price history (for all/most countries) for Convoy S21A SST40 Flashlight.
Price records source(s): Gearbest, 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)).