Both of the above are correct, but just wanted to note that the ones on Main St have in the past been a little larger, along with being a bit more expensive. One our last trip, I got one at Sleepy Hollow, then my wife got one on Main St. that definitely got a "wow" reaction from me.
Note that the smaller one is still plenty large.
And you can also get them at Animal Kingdom. In the past, they were along the path heading up toward Harambe, but before you cross the bridge. With all the changes, they could be somewhere else now.
So I would assume they can be found in all four parks. Quick search looks like TasteTrack (near Test Track) and Hollywood Scoops (Sunset Blvd) have them at the other two parks. (TouringPlans shows them at DinoBites in AK, which isn't my earlier description, but is in DinoLand.)