Use two Magnets.. or a magnet and a screw.
alternately, get one 3D printed. It won't come with the screw, but that isn't a huge obstacle. 
I recently Gorilla glued a magnet to the back of an Iris v2 Motion Sensor and using a 3M Command strip, a washer to the wall. Previously I had used the Command Strip to adhere the sensor directly, but after one battery change too many, I decided to try this. It worked but it looked insecure since the magnet would slide to the end of the washer and more or less hang from the edge. So I bought a set of small magnets and with a Command Strip, put that on the wall. Perfect, so far. 
I bought these so that you don't have to be tempted.
They are perfect EXCEPT they are astonishingly fragile. I opened the shipping package and my kid asked what they were. I peeled one off and handed it to her. She wanted to see if it would attract through the thickness of her hand... it couldn't but when she put it on her fingers, it wormed between them and clicked onto the full set... snapping in half. So, do NOT buy these. There has to be a better set than this. It works perfectly in the intended application and as long as I take great care, it will do what I need for years. I use a "rolling" motion to get the magnet on the Motion Sensor to connect to the one on the wall.
Note that in my case I'm using two different brands of magnet, it's only the wall mounted one that is this fragile thing. Another failure with these magnets is the words claim there are 10 north magnets and 10 south.. so that the two countersunk screws would face each other in use.. false. They are all one direction. Not problem for me since I'm using Glue on one side and don't need the screw.
Although this is the Iris V2, the results would be the same. In the above pic, the tiny (fragile) magnet is as close to the sensor as I dare get. Any closer and...
I hate for this to get longer but here's the Motion Sensor up on the wall...
and this is the wall mounted magnet.
