I use a plastic sandwich bag 😳
I travel most places by bike, clothing varies and my cards/cash are one thing I don’t like to put in or leave in a bag so are always on my person.
I hate bulky wallets or anything that starts to feel heavy weighing a pocket down or being the wrong shape to fit in so just keep my cards (4 of them) in a plastic sandwich bag, along with a fiver or a tenner, it’s light, waterproof and not at all bulky and works for me.
I also get to enjoy ‘new bag day’ every month or so when the old one has a hole in it 🙂
Another side effect is that it seems to wind everyone up, family, co-workers, friends, I’ve lost count of the amount of times they’ve offreed to buy me a wallet for my birthday or something, but it doesn’t seem to register that I’ve chosen not to use one, I’m perfectly capable and financially solvent enough to buy a wallet if I wanted one!