Chalk Holder A College Teacher Needs Help - Alergic To Chalk.?

A college teacher needs help - alergic to chalk.? - chalk holder

I taught at a private school and are allergic to chalk.
I remember I saw a US-American teacher uses chalk holders. It was like a mechanical pencil, insert a pencil and chalk on the Botton is pressed at the other end. The chalk is the length of desire.
I'm looking for this kind of chalk holders in vain. Has anyone an idea if the teachers are using this way? Or is there someone allergic to chalk and how he / she solve this problem. It itches.