I've created this model partly to protect the tag from damage, partly to prevent the back cover to fall off but mostly so that the tag doesn't turn itself off in my Pocket. The Freecad-File is included if you need to adjust the fit - the included spreadsheet contains variables for the thin part (aka the sides), the thick part (aka the middle) and the diameter the tolerance is also added to every side meaning that a tolerance of 0.1mm will make the whole shell 0.2mm thicker overall.

If you print the shell on the side where you press the tag in you should be able to get away with 0 support.

You should still be able to turn the tag on and off by pressing just next to the shell.

Happy printing!