Aliexpress
Click here… to search for Xiaomi ZMI QB821 20000mAh Power Bank on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. I couldn’t find any coupon for this product on latest product update.
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): zmixiao, zmiqb1, zmi8211, 21QB821, HU19142, aff7off, e2bcea, BGZMIQB821, BG3CSUM, bgssaff9, BGPAYPALSS, BGaDmITAd, BGBFAFF2019, BGCITYADS2019, 2020CNY, BGVDay10%off, BGXMI15, BGdragonBoat, BGAFF10OFF, bgshOOp10, BgoFErTaSchInA10, BgcLuBofErtA10, BG15POWERBANK, BGCuponation10, 13f142, BGHONEY2110
(probably won’t work, but you can try them out)
Price history and price alert
Do you need price history chart (for all/most countries) for Xiaomi ZMI QB821 20000mAh Power Bank? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).