I have designed a plotter tool head to hold either a sharpie or pen. This holder bolts to a standard Taz 5 extruder mount. I have included the lulzbot mount, outer housing, and two different inner slides. The two slides are sized to fit Sharpie or Bic pen.

After printing, screw the housing to the toolhead with a pair of screws and insert the desired slide and a .750" OD x .625" ID spring at least 1.500" lg. I found the spring at a local hardware store. Swap the extruder with this head and insert a 100k resistor in the socket that would attach to the thermistor. Home the Z axis and then raise the tool 1 mm. Insert a pen from the top and tighten the front screw to lock the pen in place.

To generate the gcode I used the instructions at https://medium.com/@urish/how-to-turn-your-3d-printer-into-a-plotter-in-one-hour-d6fe14559f1a and begin at Step 3