…so, after a couple of years of trying to leave the idea aside, I finally bought a 3D printer. I'm really amazing how good is a cheap printer (€217) nowadays, and how easy it was to set it up. In the first concave prints I had lots of stringing, which I solved as suggested by CHEP. So, yes, now I own a 118dB whistle and I don't even know why. :P You can follow my experiments in this Google Photos album:
Maybe some slight mods, e.g. in the case of this fidget I flipped some pieces upside down to avoid needing support beams. Also for some (yet unknown) reasons one of the two bigger gears failed to print, so I duplicated the other one and mirrored it. Opensource Slic3r-PE allows this stuff easily.