If you have the guild open, you can buy a new one there. You can also find them fishing and you'll get more in the mines, but that is hard to do without one.
If you still have the "Kill 10 slimes to prove you're an adventurer" quest open, use the scythe to kill the green slimes. It doesn't do much damage but it works.
Axe and pickaxe also work, but the scythe does not use energy and it has a bigger hit box because of the swinging motion.