I have just checked coupons. The lowest price I could get is $20.49 for Xiaomi Mijia Hygrometer Thermometer Pro (in Banggood). Get coupons, create price alert or check price history out! Let’s see what best price is ATM.
Xiaomi Mijia Smart Temperature Humidity Pro Electronic Digital Clock Watch E-link Thermometer Moisture Meter Work Mi Home
Latest coupon code price check (UTC time):
Banggood ($20.49)
Banggood warehouse is located in China. I can’t find any active coupons for this product in Banggood. The question is – is it a good price? Maybe there’re no more promotions for this item, because current price is higher than average (which is equal $16.94)
Link: Banggood product page
Price: $20.49
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BG81309f, BGM1TOOLS88, BG05f151, BG20236Tool, BGTOOS729, BG31a67a
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Check out price history chart (for all/most countries) for Xiaomi Mijia Hygrometer Thermometer Pro.
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)).