Sorry to resurect a year old thread (it came up when I searched for chalk pens in NZ!). What did you end up buying? I am looking on ebay and there are some for mega cheap (US1.80 with free shipping!!) but they have this disclaimer on the bottom of the page:
Please note:This fluorescent pen can be used as chalk to write on the board,however,it can not display its color well,so it's better for you not to use it like this.
For that price I think I'll just buy one to try anyway, but thought I'd check here first in case you ladies had bought that kind