(UPDATES)
*I made the spring a bit harder to press so that the pen doesn't wobble around too much, added a M3 nut housing to make the screwing easier.

This is a part to add to the Ender 3 Hero Me gen2 fanduct. it screws in place where the leveling sensor should go and it can stay attached even when not in use.

You can add a pen to it and tighten it up with the screw, you need an M3 bolt and nut to fix the pen and to fix the printed part you can reuse the stock screws.

I suggest having the tip of the pen 2MM below the nozzle and adding a Z offset so that the pen doesn't crash in the bed.

You have to find the optimal z height for your pen so that it gets pushed down a bit, i used a -0.4mm height, and for that reason i used a Z offset of 1.6mm, you also need to add a 4.5cm X offset so that the pen is centered.

I used this to generate the Stl file from a picture https://www.thingiverse.com/thing:66115 .
Use "Target Height 1mm ; Add base 0mm ; Max Res 0.1mm" and then play with the B/W threshold to your preferences. in case that the output file is low quality, i suggest using http://waifu2x.udp.jp/ to upscale the image 2X and putting the "Target size" to an high value and then scaling it down in the slicer.

This is the profile i used for the plotter itself, make the stl file of the picture 1MM tall so that it makes only a single 0.1mm layer.
https://drive.google.com/uc?export=download&id=1YUh12s8gIQ3uIC2LWAs3iwWXE5MP2u-A

You can print the mount without support but i suggest to use "0.39" line width to help the slicer with the spring.

After printing you have to remove the supports i added.