These four parts will replace the laser-cut plywood parts on the Eggbot. All three major components are compatable with the wooden parts, so you could just change out the pen holder it would work fine. The plastic parts make the penholder much more stable. The penholder is designed to work with the Sharpie and Sharpie Micro. When changing pens, the alignment should be right on the spot.
Print the parts. The Eggbot is a mix of SAE and Metric hardware. The nut in the Coupler is 5mm. The nut that is pressed into the Pen Holder is 6-32, to match the old thumb screw. The flexure Is held to the Pen Holder with the same screws as the original used, but the 6-32 screw that held the Arm side has been changed to 3mm (or #4). This was done because the new design uses a nut, and it had to be small. The little plate speads the stress on the top of the flexure, just as the angle plate had done.
Oops, I noticed that the Coupler is upside down in the photo. The PDF shows the proper way to assemble it.