Next time you are out and about in the middle of a stand of Betula cast about for a bracket fungi that looks like this.
It's called Piptopourus Betulinus or Razor Strop.A very useful thing indeed.Take it home and carefully remove the pours underneath the fungi with a sharp edge tool,remove the uppermost layer,and you will end up with something akin to this.
Dry the fungi slowly and carefully,plenty of air,and when you are happy.........STROP! It's an extremely light and hard wearing material,I have used this one for many years.