This humidifier is simple to print with no supports.  Print the body upside down with the opening on the bottom, and the lid with the retaining tabs pointing up.  I printed at .16MM later height and 50% infill, but it ends up being pretty solid with inner and outer walls.  I printed in MatterHacker's Build Red filament.  For the inside media I ordered Melamine Sponge material (think Magic Eraser)  and trimmed to fit.  I did tune up the clips on the lid with a light blast from a heat gun and tweaking them to provide the desired grip.  This humidifier seems  to be very comparable to purchased ones.  Just wet the sponge as needed to control humidity.  See it on Thingiverse! 

Downloads

STLGuitar Humid (zip)

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F3D Guitar Humid (zip)

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