Buy it from the Traveling Cart in Cindersap Forest when it appears
Purchase it from the Desert Trader on Thursdays in exchange for a Lucky Lunch
Get it as a random drop from a Serpent in Skull Cavern
Get it as a random drop from a Witch’s Hut event involving a rabbit
Raise a rabbit in a Deluxe Coop and wait for it to produce one
Increase friendship with your rabbit so it may give one as a daily gift
Check the Traveling Cart regularly for the best early-game chance