Neodymium magnets are the strongest type of permanent magnet commercially available. And we added two!
This water tight box with twin magnets is great for holding and protecting your GPS Tracker. Its inside dimensions (3.2x1.5x1.8 inches) will hold the best trackers. (View Images)
Used by law enforcement and private detectives, it is surely going to work for your application.
Please notice that this is an empty box, not a GPS Tracker.