86type: 86 * 86 * 37mm.
Basically copy coupon, view price history or create e-mail price alert. What is the best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. I couldn’t find any coupon for this product on latest product update.
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!
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): aff7off, 12annvex-8%, elec, e2bcea, 502C6B, 13f142, 6GSGIT, BG15Sonoff
(there’s a little possibility that old coupon will work)
Price history and price alert
Price history (for all/most countries) for SONOFF AC90 To 250V 400W Touch Wifi Switch EU is here. The lowest price was: $9.51.
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)).