Aliexpress
Click here… to search for 4x Panasonic NCR18650B Battery on 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 (28.99 USD): BANGGOODSD
(CouponsFromChina.com tip: put item in your cart and apply coupon code there 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): 2019FG, 2019fg, BGF1111, fInbG2020, BGff2020, BCNLXK, BGSM30%, BG1128, BG10OFFAFF1, BGFLBA
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Price history (for all/most countries) for 4x Panasonic NCR18650B Battery is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).