You can get it in the house next to "Mossdeep Space Center" in Mossdeep City.

HOUSE NEAR MOSDEEP CENTER TALK TO THE SAILOR AND HE WILL GIVE YOU ONE
HAPPY FISHING!!!!!!!!!!!!!!!!!!!!
KE EPISIS GIANNITSA
OLLLLLLLEEEEEEE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!

go to mossdeep city and go up the stairs like you're going to the space center but go to
the left and keep going to you see a fisherman there will be a house go in and talk to the
man