I bought a small compass in Akihabara for this reason - my phone was old and unreliable (it would often send me in the completely wrong direction - claiming "no

I bought a small compass in Akihabara for this reason - my phone was old and unreliable (it would often send me in the completely wrong direction - claiming "north' was really "southeast") and it was a lifesaver. I could look at map, see I need to go east, look at my compass really fast, then go east. I wore it on my keychain - and I still do! Doesn't come in handy as much since I know where I'm going but it's nice to carry around.