Zippered leather wallet
Elastic fabric assorted sizes from 1/4" to 1" wide, black
Coins or cash
Little pocket knife
LED keychain light
Emergency contacts card (laminated)
...whatever your imagination can fit in there. My favourite is the Swiss Card (the green thing) that has a bunch of things in one little package.
I started by taking the innards out of the wallet. This meant clipping the stitching around and leaving only the backing card. Be careful not to take the stitching that goes to the outside of the wallet. Collect the things that you will be interested in putting inside and start placing the elastic pieces in. Hot glue and scissors and a little planning are all that is required here.
Be careful not to get any hot glue on the zipper as it will become hard to close/open later.
See pictures for details. I wanted to keep a coin or two as hopping carts seem to need these when I never have one handy. I reserved the top right corner so the angled elastic is there. This angled elastic is also used to hold the back cover of the notebook in.
It's mighty small and fits into the interior pocket very handily. You may want to look at a GPS case or Maxpedition's models if you are a serious getter-outter and want to put more stuff in it.