You can see my model (orange) next to the original (black) in the photo.
Design features
Modelled based on the original extension nozzle included with my X3 fan
Wind speed measures nearly the same as the original (within 3% in my tests)
Printing instructions
Print the .stl file as oriented, in flex with maximum 20% infill.
Usage instructions
Squeeze the large end and insert it into the existing removable duct (see picture)
To remove, pinch the large end and pull
Notes
I designed this model in OpenSCAD and it's fully parameterized. If you'd like a simple modification (i.e., nozzle length or diameter), send me a message and I'll see what I can do.