Aliexpress
Click here… to search for 4x Panasonic NCR18650B 3400mAh Protected Battery on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. There are no coupons for this product in Banggood.
Link: Banggood product page
Price: -3 USD
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
Old coupons (from the oldest to the newest): CMB3, AC18, 2019FG, BGF1111, BGff2020, BGSM30%, BGTBD, BG1128, BGFLBA, BG10OFFAFF1, BANGGOODSD
(these coupons are old, so probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for 4x Panasonic NCR18650B 3400mAh Protected Battery.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).