Recently I bought myself a mighty wallet since I liked the idea of a nice thin alternative for my conventional leather wallet. However, I live in Europe and you really need a coin pouch around here here. Firstly I was a bit annoyed that they don't offer one with such a feature. But than, I found out that its easy to built one using just the packaging that came with it. Since the hanger is also made from Tyvek, it should be just as durable as the rest of the wallet.
At first cut off the hanger as a template. Because the hanger just happens to be slightly narrower than the wallet, It will allow to fit the pouch snugly in one of the side openings of the wallet.
Use the template to mark the desired width of the pouch. Starting from the lower end of the text block.
Fold it at this marks and flip it over.
Attach some adhesive film at the end of the ribbon at the blank side.
Form the pouch and secure it using the adhesive film at its inside.
Flip it over and fold the rest of it under a 45° angle.
You want to be sure that this fold is firm, than apply some adhesive film over the two holes by the hanger.
Flip it over again and use the adhesive covered holes to stick this side to the back of the pouch. If you've done it right, the pouch is now closed form 3 sides.
Flip it over and use the rest of the sheet to form a flap. I've decided to stay with a rectangular shape and 2 layers of material.
Apply some glue to the flap and glue it in place.
Now your coin pouch is finished. Not actually an eye catcher but it will do the job.
Insert the pouch in the side-opening of your wallet and fill it with coins.
Close the flap and you are good to go.