Brush Pen
Brush Pen Tip Allows for Thick and Thin Lines in One Expressive Tool
Brush Pens are the tool for you offering deep rich black color and varying lines widths depending on applied pressure.
Funwari Brush Pen Single Ended Super Fine

The brush tip has the control of a regular marker with just enough spring for thick and thin lines and control.
Zensations Brush Pen

Zebra Brush pens are the tool for you offering deep rich black color and varying lines widths depending on applied pressure.