I have modified the movement system from itsaMeWolf's design with a higher focus on eliminating play between parts. The dove tail is now designed to be printed in the horizontal plane and should made with ironing enabled (see 3mf and gcode files). Additionally the pen location is moved closer to the nozzle to increase usable plotting area.

What you need

4x M3 8mm bolts 

2x washers for the interface layer between the heatsink (or you could print them files are also included)

Rubber band (you have two options for its positioning either on the grove in the model or the top of the pen) In general just make sure minimal force is applied.

Setting up

I suggest following the instructions present in this model's description 

https://www.printables.com/model/252731-prusa-mini-pen-plotter

Warnings

DO NOT PRINT WITH THE ATTACHMENT ON (I intentionally printed mine in red so I don't forget)

REMOVE PEN HOLDER PART WHEN HOMING (you can keep the mount part on)