Embedding entry sensor magnet in the door frame

I have 2 door frames in my home that are very deep and there is no clear way to mount the magnet without it getting sheared off when the door is opened.

The installers of an old ADT alarm system (which my SS system is replacing) chiseled a notch in the frame and broke open the magnet container, removed the metal part and hammered it into the notch.

I'd like to do something a little nicer. I can route out a magnet size hole, but what would be really nice would be to have a magnet that is packaged to be embedded flush with the wall. I could easily imagine something like this existing, but I can't find it anywhere online.

Anyone else fine a good solution to this problem?