Get a yellow duster,fold it, wrap it well in foil, chuck it on the fire, leave for a while(10 mins ish) fish out, let it cool and unwrap your charcloth.
Lots of other ways, substitute denim or any other cotton cloth for yellow duster.
Substitute a coke or beer can folded over for foil or use a sweet tin. As long as the container allows in heat and not oxygen, but be aware gases need to escape, you are sorted.