While not a "large" repository, a polished Altoid's Tin would provide some storage and signaling ability.

You might also consider folding an aluminum bread "pan" (available at WalMart for $1.88) to allow for water boiling. I've tested this method, and its good for one fold / unfold before it leaks.

JYD #123 The great one formerly known as Architect.

I am now a fictional British television police officer (currently a Detective Sgt) at Thames Valley Station. My governor is Detective Inspector Fred Thursday and it’s 1969.