Aliexpress
Click here… to search for Qingping Bluetooth 5.0 Mijia Temperature Humidity Sensor on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. I am tired of searching coupons, but I found one for you…
Link: Banggood product page
Coupon (13.99 USD): BGGRMA162
(CouponsFromChina.com tip: put item in your cart and apply coupon code there 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): BGe43f20, BGSHE15, 13f142, BGTYOC535, BGIS535, BGAU535, BGHUOB535, BGSPO535, BGHUOY535, BGTYDB535, BGTYOL535, BGXPJA128, BGXPJA129, BG00c906, BGHealth10D, 2022ACTIESNL, BGHB218, BGMAYB239
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for Qingping Bluetooth 5.0 Mijia Temperature Humidity Sensor is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).