You can create price alert here, copy coupons and view price history. Let’s see what best price is ATM.
Color: Dim Gray, Casing material: PC V0, Work temperature: 0°C-40°C, Button quantity: 6, Dimension: 86x86x13.5mm, Battery model: CR2032
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):
Banggood
Banggood warehouse is located in China. There are no active coupons for this product, but the price is pretty low isn’t it?
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): BGJUNEGSG9, BG15Sonoff, TTSUMMER8, Cuponation9, 9OFFSUMMER, BGsonoff30, BGa044d8
(these coupons are old, so probably won’t work)
Price history and price alert
Check out price history chart (for all/most countries) for SONOFF SwitchMan R5 Smart Scene Controller.
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)).