yellow, Color Black, Fabric Polyester, Capacity 15L, light green, Dimensions 390x 270x 150mm, Weight 206g, Lining Polyester fiber, pink.
Just check coupons out (with price alert and history). What is best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. There is one coupon available! Pretty cool, huh?
Link: Banggood product page
1. ($20.69): BGTY704CP
apply code in your basket (cart) after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BG412YU, bGhOnEy10, BGAFF10OFF, BGdragonBoat, BGCAMP01, BGSDJKJ5, aa6f59, bgshOOp10, BgoFErTaSchInA10, BGXMBAGG2, BGSHHA, BgcLuBofErtA10, BGZPBC15, BGCuponation10, 13f142, BG10OFFAFF, BGwhielabel
(probably won’t work, but you can try them out)
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. Europe – Xiaomi 15L Backpack [EU] ($-3)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi 15L Backpack. The lowest price was: $12.99.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).