From Merchant & Mills:
We have made this useful little bag from oilskin. Sling it over your shoulder and keep your little essentials safe and close - ideal for the passport, tickets and keys. With this project you will get to make a strap from scratch and fix an eyelet to attach it to. Small as it is, the make of the document bag requires some skill and concentration. On the bright side, oilskin is very easy to sew as it is very stable and topstitches well.