Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (592.92 USD): Terence
Coupon (592.92 USD): 2203ActiesNL
Coupon (599.30 USD): BG00c906
(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): BGHOMEA13, 7bcdf9, BGCuponation10, BG10OFFAFF, BGwhielabel, BG10OFFAFF1, 6GSGIT, 00c906, ADMITAD2212, 2022ACTIESNL, Tabby20
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Here is price history (for all/most countries) for Xiaomi MR442-A Water Purifier H400G.
Price records source(s): Banggood
Click on image to enlarge.
You can set price alert (for Banggood).