Aliexpress
Click here… to search for Xiaomi Mijia AirPOP PM2.5 Mask on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. You can get coupon down below.
Link: Banggood product page
Coupon (8.59 USD): BGAFF10OFF
(CouponsFromChina.com tip: apply it 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): f0f958, 502C6B, 3229b5, elec, TOOLS15, BGAirPOP, BGCITYADS2019, AFfbG10, BGELIG0920
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Do you need price history chart (for all/most countries) for Xiaomi Mijia AirPOP PM2.5 Mask? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).