If you would like to learn how to make your own whistle you should check out my YouTube channel where I made a step by step tutorial.   The entire project should take you about 15 minutes.  I have created videos walking through the process in both 3d design and codeblocks so you can choose whichever you find easier.

I printed my whistles with a .4mm nozzle, 3 walls, and no supports.  I found an infill of 10% with lightning infill was adequate.  The three walls helps ensure that there are no gaps and you whistle functions perfectly.