Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. There is one coupon right now! Check this out.
Link: Banggood product page
Coupon (38.29 USD): 00c906
(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): BG90FUN235, AFfbG10, BGBFAFF2019, BGCITYADS2019, BGBGHFRI15, BGVDay10%off, BGSPR, BGHOMEG12, BGAFF10OFF, bGhOnEy10, BGBSBJP, SKUA66474, BGdragonBoat, BGSS10%SW, bgshOOp10, BGHome15%, BGHOMEA15%, BgcLuBofErtA10, BGNOTD474, BGDEAL474, BGCuponation10, 13f142, BGHONEY2110, BG10OFFAFF, BGwhielabel, BGJUN164, BG10OFFAFF1, BGISOC73, BANGGOODSD
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for Xiaomi Youpin 90FUN School Bag is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).