Or a CD. An Oregon sheriff on search and rescue showed a group of us that
trick. He used an AOL advertising CD with the sides shaved off to make it
conveniently small (though still bigger than the usual signal mirror.) Easy
to use, free, and much lighter than the double-glass ones usually sold for
the purpose.

Good idea, but you need to include the hole, or make a hole, and learn
how to use that hole to aim the "flash" where you need it.

vince norris