What country are you in? The device selection does vary. 
Also, do you need the individual sensors to have an audible alarm, or not? Some models do, some don’t.
Linkind has recently become popular in the community because they are inexpensive and there is a community created edge driver that works with them. They use Zigbee.
At the time of this writing, the four pack was about $50, but there’s also a 20% off coupon on the page.
Here’s the edge driver: