Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (9.99 USD): BGcaa3e6
Coupon (13.80 USD): BG1efeb0
Coupon (13.95 USD): Terence
Coupon (13.95 USD): 2203ActiesNL
Coupon (14.10 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): BGOOR3WW, BgcLuBofErtA10, BGZKHDW1, BGTEST37, BGAFF10OFF, BGGDJUT7, BGTESCN02, BGHONEY2110, BGAP2803, BGwhielabel, 13f142, BGAU0407, BG10OFFAFF1, BANGGOODSD, 00c906, ADMITAD2212, BGAlerabat1
(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 Smart Sensor Plant Flower Monitor? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).