Ultralight image stabilizer
Is there blurring in most frames?  (i.e. if you pause it, do most of the still frames that make up the video look ok on their own?)

If the shaking didn't blur out your image too badly, you might be able to recover something usable with ffmpeg's vid.stab filter.  It has some parameters, like speed of camera moves to not count as shake.

IDK how it compares to what iMovie has, but if your video keeps some of what you want in-frame most of the time, and isn't blurred to hell, software should be able to give you something.  (cropped to contain just the part that the camera kept in-shot for most of the frames).