Check coupons or create price alert down below. Let’s see what best price is ATM.
Frequency: 868.4MHz, Battery life: 2 years, Powered by 1x button battery (installed), Compatible with 300 series and 500 series
Aliexpress
I could not find it on Aliexpress. Click here to search by yourself.
Here are coupons that you can use.
Latest price update (UTC time):
Price history and price alert
Price history (for all/most countries) for GC00AM NAS-DS01Z Door Window Sensor is here.
Price records source(s): Gearbest
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)).