I created a very nice 3d tic tac toes game, in its own case.

It makes tic tac toe challenging again!

In the FREECAD files there is a quick printing magnet holder model to size magnets of your choice.

  I found that rod magnets, with the poles on opposite ends work best.

    Change the magnet holder parameters to suit your needs.   

    Print a quick test print

    Cover the plastic & the magnet with a rag, then use a pair of pliers to snap the magnet in.

    They should snap in readily, but firmly.

    Don't forget to transfer the new parameters into the CAD files for the tic tac toe set, and re-export the model.