Dimension: 35X39X28mm, Battery: 3V(CR2450);, Wireless protocol: ZB (IEEE 802.15.4);, Material: PC;.
Check coupons or create price alert down below. 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. Too bad there’s no coupon right now in Banggood.
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): BGSONOFF15, BGSNZB03, BgcLuBofErtA10, BGSONOFF16, BGSTHO15, BGHONEY2110, BGSHOM15, 13f142, 6GSGIT, pROMo8cuPoN, BGJUNEGSG9, BG15Sonoff, TTSUMMER8, Cuponation9, 9OFFSUMMER, BG6edee4, BGfac6fd
(there’s a little possibility that old coupon will work)
Price history and price alert
Do you need price history chart (for all/most countries) for SONOFF SNZB-03-ZB Motion Sensor? There we go. The lowest price was: $4.99.
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)).