While they are sold at multiple locations, there are pins for each park (and often the resorts). They can be bought at locations outside of the park, but I like collecting pins of the places I've visited. I don't know if they are in stock, but each of the parks is supposed to have their own Starbucks mug that cannot be purchased at any location outside of that park. For Epcot, there is merchandise that is unique to each WS pavilion (e.g., the Pick-a-Pearl mentioned by grammimouse, along with things that say "Epcot" on it - like the flag magnets, pens, pins, etc.). Figment merchandise is largely only available at the Imageworks in Epcot.