Have you seen this thread?
I know it's at risk of being "outdated" by now, but with only a few months left in the year, maybe they'll do another one soon. 
The community favorite there, the Iris v2 (and v3, I guess...) sensors, are long discontinued--and were then, too--but I guess that goes to show how much people liked them. I'm a fan of the CentraLite Micro motion sensor as a similar replacement, and it got a few votes there. They are about the same price Iris sensors were when they were at their lowest new price, $30 USD, though Ezlo (their new owner) often has sales, maybe more around the fall and winter holidays in the US.
I'm sure the SmartThings Motion Sensor, now sold by Aeotec, is as good as it was before, but for $40, I'm not about to find out. (Still reasonable by Aeotec prices, though!) Hue is also great, but again, more expensive than some others.
For cheaper options, I've tried Sonoff but also wasn't impressed. I do like the ThirdReality sensors mentioned above, and they're also pretty inexpensive. They just don't look quite as nice, and I haven't had them long enough to comment on reliability. They are just motion only, but the "extra" features like temperature in a motion sensor aren't always a concern for everyone.
Looks like you're in Canada, though, so what you can get--and how much it costs--is likely different than the US. These are just a few things I'd look at if I had to by more motion sensors today.
