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 (127.50 USD): BG1efeb0
Coupon (128.89 USD): Terence
Coupon (128.89 USD): 2203ActiesNL
Coupon (130.27 USD): BG00c906
(CouponsFromChina.com tip: this code has to be applied 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): bgshOOp10, BGMJJSQ03DY, BGHome15%, BGHOMEAPP13, BGHOMEA13, bGhOnEy10, BGQ03DYRS, 7bcdf9, BGCuponation10, BG10OFFAFF, BGwhielabel, BG10OFFAFF1, 6GSGIT, 00c906, ADMITAD2212, 2022ACTIESNL, Tabby20
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Check out price history chart (for all/most countries) for Xiaomi Mijia MJJSQ03DY Humidifier S 4.5L.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).