Herman Miller Aeron Arm Rest Support - Improved - No screws!
thingiverse
I remade @candrist's design from scratch, and added a customizable arm height. This piece just goes inside the arm rest (see picture). It should fit snug, and will hold the armrest at that position. If yours doesn't fit right or is too loose, then edit interior_height and interior_width to your needs.
Download Model from thingiverse
With this file you will be able to print Herman Miller Aeron Arm Rest Support - Improved - No screws! with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Herman Miller Aeron Arm Rest Support - Improved - No screws!.