Aliexpress
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Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. You can get coupon down below.
Link: Banggood product page
Coupon (24.53 USD): BGHealth06
(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): BGXIAODA1, BGSL18, 0e7f33, BGHPHC, BGHPB7, BGHB20, bGhOnEy10, BGSD25698, BgcLuBofErtA10, BG49660, 13f142, BGCuponation10, BG10OFFAFF, BGwhielabel, BGjune53, BGjune98, BG10OFFAFF1, BG4dac98, BANGGOODSD
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for Xiaomi Smartda Sterilizer UV Ozone Antivirus Lamp is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).