Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (13.61 USD): BGAFF10OFF
Coupon (13.61 USD): BGTT10
Coupon (13.61 USD): bGhOnEy10
Coupon (13.61 USD): bgshOOp10
Coupon (13.61 USD): BgoFErTaSchInA10
(CouponsFromChina.com tip: you should apply the coupon 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): 2019SPEDM, BGXmund10, AFfbG10, BGXD6, BGX656, BGOL786, BGdragonBoat, BGCAMP01
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Here is price history (for all/most countries) for Xmund XD-DY3 18L Backpack.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).