Balcony railing mount

It might require some sanding in case you have overhang issues. 
15% infill

Snaps on are pretty solid. Easy to install and remove if needed.
Don't forget to either increase the length of the bar or print alternative one. 

An alternative way to mount a windmill is a snap-on balcony rail mount.
Contains slightly longer bar to make sure blades do not touch the rail.