The original whistle comes from MikeP-NZ: https://www.thingiverse.com/thing:77183 I just made some accessories for it. The mouthpiece makes it easy for children to use (but never give a whistle to a child or everybody will get crazy!) It has a small ridge so you can hold it with your teeth. Of course, check what filament and glue you use before putting it in your mouth. The necklace thing makes it always ready to use. I used a bit of 3mm flex filament as the "string".