I've spent the day making a carrier bag for a german friend who is visiting us these days. It is quite time consuming to sew one like this, but it's worth it. The bag is nice and proper done. Inside there is a pocket with a zipper and one for the cell phone. I also made a chain with a carbine hook to fasten the key in.
I have one of those myself and they are very practical.
As you can see at the pictures there is a big pocket on either side of the bag. Since they are outside the bag I have chosen to make a loop and use a button to lock them up.
I use mine when shoping, for hand luggage when traveling and when going to work.
They are easy to make but as I said time flies when making them.
Have a nice weekend.