I can think of the following two ways to cover the blade:
- You can use something like a Bike Handle cover, the one that has a cap on the other end. You can get it of the size that your axe-blade fits in. I assume that the main blade will be a bit hard to fit in, but then you can always give a try towards getting the handle cover which is a bit flexible(probably made of vulcanized rubber?)
- You could get a leather packet sewed/tailored to fit the blade in. Provide some kind of a sling-thread thing to wrap around it?