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 (17.87 USD): Cuponation9
Coupon (18.07 USD): TTSUMMER8
Coupon (18.46 USD): BG00c906
(CouponsFromChina.com tip: apply code in your basket (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): 502c6b, 502C6B, 1888CODE, PICODICOM, e7cac7, 2019SPEDM, AFfbG10, BGSO899, BGSO799, BGCITYADS2019, BGVDay10%off, BGHOMEG12, BGAFF10OFF, bGhOnEy10, BGSOTHING25, bgshOOp10, BGHome15%, BGHOMEA15%, BgcLuBofErtA10, BGCuponation10, 13f142, BGHONEY2110, BG10OFFAFF, BGwhielabel, BG10OFFAFF1, BANGGOODSD, 00c906, BGAlerabat1, Terence, Tabby20, 2203ActiesNL, BG1efeb0, MVC8SPRING, 8BGwbg2204, tRaDetRaCKeR, 8wEbgaInS5, pROMo8cuPoN, BGJUNEGSG9
(probably won’t work, but you can try them out)
Price history and price alert
Do you need price history chart (for all/most countries) for Xiaomi SOTHING Geometry Humidifier 260ml? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).