I designed a better pen holder for the Ender 3 (tested on OG and V2). It's fully printable, although I used an M4 bolt/nut and some rubber bands. 

4 files are included: 
 

• Mount 
• Pen holder 
• Z shim - allows printhead to stay above the build plate
• Gauge - to align the pen tip to the correct depth

By default the tolerances should allow smooth movement of the pen holder. The gauge and z shim cause Z0 to be 3mm below the paper, which gives good contact.

You can also print the pen holder with tight tolerances and allow no movement in the Z direction. In this case you need to adjust the pen tip location accordingly, but I found that I prefer this way. 

I made this in Tinkercad, so I don't have any other files available.