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 (15.07 USD): AFfbG10
Coupon (15.07 USD): affbg10
Coupon (15.57 USD): aff7off
(CouponsFromChina.com tip: this code has to be applied in your cart 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): rchobbies8, CFadmitad, e2bcea, TTxBG10, BG10EA
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for 5x Eachine H8 Mini H8 RC Battery 3.7V 260mAh is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).