Kydex would be a decent option as well, if not a bit more on the expensive side of things.If I was going to make a specialized backpack for toting my woodsman tools, I'd find a pack frame worthy of modifying, then I would build custom scabbards out of some heavy duty leather. Leather is a lot lighter than wood and would make a more practical scabbard. You wouldn't need to worry about splitting it, should it get dropped or slammed around a bit.
I suspect that a leather scabbard would just be preserved by some spilled oil, whereas a wood scabbard would look like a mess.