A firend of mine has broken one of the external skin part of the wonderful Ikea PS2014 lamp, here a 3D printed replacement part, it is not perfect but It make the job I think.
Edit 2019-01-10: A new version (ended with v6) wich is exactly the same except I changed the thickness by adding 1 mm which could make it stronger without affecting the look. I didn't try printing yet this version. I changed also the settings when exporting from fusion 3D to have better quality (High instead of Medium) which lead to less polygones
Edit 2019-01-14: add 2nd plate (Plate_B), warning I don't print it yet, it is not tested, thanks for your comments if you do. Thanks to Yunch for his pictures
Grossiste 3D PLA
Printed vertically with support, and Brim, you can remove support in the hole that is use for fix it in the lamp (in Cura use "support touching plate)
I would advise to extract the support that clips on the arm as 1st print and make a test print to check it will suit your lamp
It was 1h40 print for me (v5)
and 2h12 for v6