Aliexpress
Click here… to search for 8x Panasonic NCR18650B 3400mAh Battery on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. You can get coupon down below.
Link: Banggood product page
Coupon (57.99 USD): BANGGOODSD
(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): e2bcea, linepayflt, EYBG, eybg, BGTORCH, BGBFCR41, bGhOnEy10, bgshOOp10, BgoFErTaSchInA10, BgcLuBofErtA10, BGCLUBOFERTA10, BGFLS15, BGAFF10OFF, BGCuponation10, 4BLF, BGHONEY2110, BG10OFFAFF, BGwhielabel, BG10OFFAFF1, BGFLBA
(probably won’t work, but you can try them out)
Price history and price alert
Check out price history chart (for all/most countries) for 8x Panasonic NCR18650B 3400mAh Battery.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).