Just check coupons out (with price alert and history). Let’s see what best price is ATM.
Output current: 90mA, Weight: 0.235Kg, Features: soft touch design / programmable, Display: LED data display, Voice control: Alexa google home, Temperature range: 5~35°C, Temperature measurement error: 0.5℃, Model: ZTRV-ZX-TV02-EN, Dimensions: 105x 90x 70mm, Name: radiator valve switch, Working voltage: 1.5V
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. I have no active coupons for you right now.
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): ADMITAD2212, BGSmart6, 8Couponsde, MVC8SPRING, 8BGwbg2204, 2203ActiesNL, tRaDetRaCKeR, 8wEbgaInS5, pROMo8cuPoN, hoNEYbGdeAlS, BGJUNEGSG9, BG8ReviTrage, Cuponation9
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Do you need price history chart (for all/most countries) for Tuya ZB Smart Home Radiator Valve? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).