These magnetic screw posts are refered to as mounting magnets or pot magnets. The Adafruit ones are 0.466" from top of the head to the top of the screw and 0.192" (~3/16") for the length of the screw. The scew portion is M3-0.5 thread from what I measured.
Since Adafruit doesn't sell these I found one company that sold something similar. http://www.kjmagnetics.com/proddetail.asp?prod=MM-C-12
I ordered 8 of them for 4 for each of my displays. They don't have standoffs for additional height but I should be able to locate those in town for M3 screw size.