Just check coupons out (with price alert and history). You probably want to know what is the best price?
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 and price update (UTC):
Power input 5V—1A, Infrared frequency 38kHz, Color Black, Wireless connection Wi-Fi IEEE 802.11 b/g/n 2.4GHz, Working temperature -10 ° C ~ 50 ° C, Net weight 133g, Product size 100x 100x 26mm, Product material PC
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($17.99): bGhOnEy10
2. ($17.99): BGSS10%SW
3. ($18.99): 13f142
apply it in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): 502C6B, 6C8E66, 6c9903, bgmh2, BGMIB2, BGOMG2, TS15prime, TISPrime01, BG14XM, PICODICOM, BGXMSSR, BGBFAFF2019, BGCITYADS2019, BGMRC, BGRCRA, BGMHPK, bGpAnDacHeCk, BGOMG4, BGRCSRA, BGHOMEAPP, bgshOOp10, BGHome15%, BGHOMEAPP13
(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 Xiaomi Mijia Wifi Remote Controller Switch? There we go.
Price records source(s): Gearbest, 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)).