Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (22.99 USD): MT81K
Coupon (28.87 USD): XJBGS
(CouponsFromChina.com tip: paste coupon code in your cart and click Apply after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): 6a3b6a
(there’s a little possibility that old coupon will work)
Price history and price alert
Here is price history (for all/most countries) for ThorFire TK18 Flashlight Batter and Charger.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).