Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. One coupon is available. Cool!
Link: Banggood product page
Coupon (18.29 USD): BGTorch4
(CouponsFromChina.com tip: coupon code has to be applied in shop’s 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): 2a1d09, AC18, MSON10, BCNLXK, fInbG2020, BGff2020, BGAFF10OFF, BGCuponation10, 4BLF, BG10OFFAFF, BGwhielabel, BG10OFFAFF1, BGFLBA, BANGGOODSD
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Here is price history (for all/most countries) for 2x Sanyo NCR18650GA 3.6V 3500mAh 10A Battery.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).