I like to think that this one is my invention:
Cut up 2 tabletennis balls into 5mm*5mm pieces, put in a well closed container, such as a 35mm film can, with 1-2ml of acetone. In a day or two, it will turn into a white creamy thing.
Stuff into a mold of your choice (a little roll of paper is great as it helps with evaporation of acetone) and dry for a week or two. What you end up with is a piece of solid plastic. Drill a hole and put on a lanyard together with your firesteel.
You can scrape it with a knife just like you would a magnesium bar. The shavings easily catch sparks any burn fierce.
enjoy!
Matjaz