theres an easy home made option, get a load of crayons, some shoe polish some tinned paint like gloss, mix anything in thats waxy then melt it together and pour it into an empty twist glue stick, put the lid on and freeze it for about 20 mins probably the best way to do it, but they only really write on rough surfaces tho but are good for sandstone and rusty metal, ive made a few but hardly use em