ditchfield,
like others have been saying you can make a small sheath for a lighter and atatch it to your keyring. I have done this and it works well. Mini bic lighters are of course the obvious choice being quite a bit smaller. I like that idea of using inner tube though, I hadn't thourght of it. It would be more water resistant and like mentioned can also be burned. I found with making sheaths for the lighters that the leather got stretched after a while so a thick leather would be the right choice for it. But then as the inner tube idea showed there are many other materials that could be used. Worth experimenting to see which type is best?
-james