Basically copy coupon, view price history or create e-mail price alert. You probably want to know what is the best price?
Working Voltage 3V-4.5V, Lumens 2550 lumens, Size 119x 37.5mm, Battery options 21700 or 18650 Li-ion battery, Weight 120g
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. There are no active coupons for this product, but the price is pretty low isn’t it?
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGSD05, EYBG, BGBSPX, BG1599, BGTORCH, AC19, cbrIDgTec, BG13TH, BGF1111, 4BLF, BGSF, BG10OFFAFF1
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for Sofirn SD05 XHP50.2 Diving Flashlight is here.
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)).