I have some Sanford Pocket Accent highlighters. There isn't any true liquid ink, it's all absorbed in these weird fiber strings....well, anyways: I broke one open to use for liquid for, but there was none so I used the fibers and stuck them in a large pen top(clear), and added some hair dye. I haven't tried it yet, and don't think it'll be anywhere near buff-proof, but it's to the point where there's liquid in the bottom, and the fiber acts to hold it in, AND work as a nib...pretty awesome.