Amazon.com: Graph'It B Brush tip Alcohol Based Markers, Set of 12 Mix Grey Colors (GI80113)
Amazon.com : Art-n-Fly Alcohol Colorless Blender Marker Dual Tip Pack of 3 - Colorless Marker Blender with Japanese Ink & Brush Tip - Clear Blending Pen for Art Illustration, Portrait, Sketching, Drawing :