At the Magic Kingdom, they are available at the Lunching Pad in Tomorrowland and at the Turkey Leg Wagon in Frontierland, across from the Country Bears.
At Epcot, there is a cart between Mouse Gear and Mission: Space in Future World, and another cart in front of the America Gardens Theatre in World Showcase.
Over at the Studios, look for Toluca Legs Turkey Company on Sunset Boulevard.
In Animal Kingdom, there is the Safari Turkey kiosk located on the east side of Discovery Island just before the bridge to Asia. However, lately it isn't always open so plan accordingly!