A micro container that is well disguised to blend in with its surroundings and only enough room for a log. Bring your own pen.
The title of this Gary Numan song gives a big clue to where this cache is hidden. A micro container that is well disguised, but not out of sight, which will help it to blend in with its surroundings. It should be completely invisible to muggles. Once you see it it will be really obvious.