Amazon.com : ColorIt Refillable Watercolor Brush Pens Set - 24 Colors with Flexible Real Brush Tips and Bonus Travel Case - Artist Quality Paint Markers for Adult Coloring Books, Painting, Calligraphy :
Pocket Refillable Brush Pen Medium by Pentel – Little Otsu
Pocket Brush Pen with 2 Black Refills — Pentel of America, Ltd.
Amazon.com: Refillable Water Color Brush Pen Set of 12 (3 Different Thicknesses & 4 of Each Size) Multi Purpose Artist Grade Watercolor Brushes for DIY Painting & Lettering