After looking at all the magnet placement tools here, I decided to design my own that is very simple and easy to print quickly.  They are just two small “sticks” with a magnet on one end.  Instead of caps, I just let the two magnets stick together. They are barely wider than the magnet so it is easy to fit them in narrow spaces.  Printing them in different colors lets you identify the positive and negative ends of the magnets.  They are for ¼ x 1/8 inch magnets, but I have included the FreeCAD file so you can make them for the different-sized magnets you might have.  A bit of CA glue in the bottom of the magnet socket will secure it in place.