Aliexpress
Click here… to search for Xiaomi Flexible USB Fan on 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 (6.01 USD): BGAFF10OFF
Coupon (6.01 USD): bGhOnEy10
(CouponsFromChina.com tip: just apply this code 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): e2bcea, TTxBG10, BG3CSUM, AFfbG10, 502C6B, BGBFAFF2019, BGCITYADS2019, BGdragonBoat
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for Xiaomi Flexible USB Fan is here.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).