As a guy who brings with me two mobile phones (one for personal use and one for corporate use), plus a wallet and some keys, I simply couldn’t go out without putting all that in a small bag.
No matter what I do, it just wouldn’t fit in my pockets or if it ever does, it will be very bulky and awkward, and your keys will be scratching your phone’s screen.
So that’s why every now and then, I get myself a clutch bag or a mini messenger bag like this one from McJim.
What’s nice about this is that it’s small and has plenty of pockets to separate your devices, wallet, keys and pens. It has separate compartments for each ensuring that they are protected.
I usually bring this to the office for more formal occasions and don’t hesitate to use it even on casual weekends. You can get this one from leading department stores nationwide.