I have a great little phone case with a zip section for holding a cash card and some change. It only cost £10 from sheepish clothing (www.sheep-is.com). It's well made, brightly-coloured and has a D ring thingy for attaching to other D rings. It fits my huge smart phone very comfortably.
Be warned, don't stray onto the hoodie pages, they are the lovely and one isn't enough (it's an expensive habit)