My son loves chewing on his shirts. I made this 'chewie' to clip onto his shirt collar so that he chews it instead. It worked.

Print out a 'chewie' in a soft material - I used Taulman 618 Nylon, and you can try a soft PLA. Print it with one shell (0 extra shells) and minimal infil (5% or 10%), so that the result is soft. Don't use ABS, since it's not food safe and you don't want your kid chewing it. At least, I didn't want my kid chewing it.

Print out a 'clips' set in a hard material - PLA is perfect. I used 3 extra shells and 20% infil.

Bend the chewie into a U shape, and insert the clips to hold it in plate. See the photo.

Slide the chewie onto the shirt collar.

You can also use the Customizer to produce whichever combination of patterns. You will need to generate two separate objects, a chewie and clips, by setting the 'print' parameter to 'chewie' and generating, then setting it to 'clips' and generating.

Or download the OpenSCAD file and add your own textures. If you do, make a derivative. I made one with a MineCraft axe.