I use a ThinkTank PocketRocket
Pixel Pocket Rocket - Think Tank
The sort of product suggested by PAXfips is too fiddly, keep it simple. Not only that, but PAXfips's product is restricted to a single type of card, I use mine with CF, XQD and SD cards.
The lanyard is also a great feature, means you can attach it to something inside your camera bag (or a belt buckle)