If you are still looking, there are at least a few...
The Logitech Circle 2 has a window mount, as does the Logitech Alert 750i.
If you feel like something more "open" and customizable, the Raspberry Pi ZeroView is a small cheap camera with suction cup window mounting.
And if you were desperate, and OK with local on-camera storage only (and/or using a phone app to view footage), you could re-purpose any number of car dashcams. Many have a "parking mode" feature which has motion detection recording, and some have sensors that are better in low light.
None are optimal solutions, of course.