... Kinda like using a Ouija board on the wall.
That is the truth. Well put.
Here are some pix as promised. The plastic one on the left has two small rare earth disk magnets. The odd little piece on the right is the magnet from a disk drive servo for the read/write heads. The plastic one cost about 15 and it works quite well I use it a fair amount. The drive servo magnet was free unless you count the cost of the drive but I was scrapping it anyway.
Depending on how good your screen is you may be able to just make out the marks where the magnets are.
The two cylinders are magnets and just slightly smaller in diameter than the magnets in the stud finder. The cylinder magnets are from the trigger for a door alarm but they do not make very good stud finders just using them to show where the business is.
The read/write heads off a disk drive. The coil works against the magnet to move the heads. The magnet is surprisingly strong considering it's modest size but even if there is only a post from a broken screw it will find it.
A good place to but rare earth magnets is Magcraft I use quite a few of them for various projects. They are pretty reasonable too - I think this tube cost about 11 or 12