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You can create price alert here, copy coupons and view price history. You probably want to know what is the best price?
Aliexpress
I could not find it on Aliexpress. Click here to search by yourself.
Here are coupons that you can use.
Latest coupon and price update (UTC):
Price history and price alert
Do you need price history chart (for all/most countries) for Nylon 10L Ultra-light Leisure Backpack? There we go. The lowest price was: $3.99.
Price records source(s): Gearbest
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)).