Any kind of oak. They're good because they don't break down as fast as thinner, more tender leaves like maples, poplars.
EVERY place in North America has oak trees within driving distance. Google 'oak species (insert state)' and find out what lives near you. Scout some possible sources as you drive to work, church, the grocery, etc.
Collect a big trash bag full when they're freshly fallen (a windy fall day), and get enough for a year.
DO NOT use any kind of conifer: pine, spruce, fir, juniper, cypress, etc. They have volatile organics which can pickle your fish! If you can't find oak, stick with any other hardwood except black walnut and wild cherry. They have secondary compounds that are toxic.