Bimoji (beautiful letter) pens from Kuretake in Japan are traditional Japanese brushes in modern marker form. The Usuzumi version features a light gray water-based ink in a bristle-type brush tip. The "Cambio" series features a continuous ink flow system with a solid barrel that doesn't require squeezing to release ink. Plus, when the ink runs out, the barrel cartridges are replaceable!
Refills available here.
1-800-736-7772
8:30 A.M.-4:30 P.M. CST Monday - Friday