You will need a zip, a piece of ribbon (about the same width as the zip)...

Cut the zip and the ribbon according to the measurement of your wrist.

Stitch the zip and ribbon together by running a line of stitch (by sewing machine is lot faster - but I hand sewn because I don't have one - Sorry for my poor workmanship!)

And add in this old fashion 'buttons' at the ends. You may use a 'zap on' method or whatever you have on hand.

You will have something like this

This is how it looks when buttons

Unzip and you can keep some pennies for urgency - like ...if your hand phone failed you! or you need a coin for something...

You can decorate it a bit with some beads or ribbons. I use some beads here as I have a lot leaf over...

There is all done!

Maybe to keep some secret message...when you discover....

Have a little help from my little model.

Have fun and have a nice day!