I use an altoids type tin for my edc and access it quite frequently for things like band-aids, safety pins etc.
I just use a cable tie over the tin and trim off the excess. It keeps the rectangular shape after a while, slips on and off easily, keeps the overloaded tin closed and resists pocket wear better than the ranger bands i've used previously.
And the cable tie is bright yellow, so it's easy to spot if i drop the tin.
You might not want to get the really big sized cable tie, you'd probably have to experiment with the size which would suit you.