Pokemon GO trainers are seeking the Dragon Scale evolutionary item.
Much like the King's Rock and Metal Coat, the Dragon Scale is a special item used to evolve certain types of Pokemon. It is among the rarer evolutionary items trainers can find—likely due to its smaller applicable Pokemon pool. After all, Dragon Scales only apply to a single Pokemon: Seadra.
Trainers can only use the Dragon Scale to turn Seadra into Kingdra along with 100 candies.
Dragon Scale Pokemon GO: How to Get
Trainers can get the Dragon Scale item the same way they get other similar evolutionary items: by spinning PokeStops. This is currently the only guaranteed way to get this item. Occasionally, research and walking rewards will feature evolutionary items. However, unfortunately for hopeful trainers, there is no surefire way to ensure the item will be a Dragon Scale.
Dragon Scales carry a 1% chance of dropping from any PokeStop. This allegedly jumps to 50% after 250 stops have been spun, but this has yet to be confirmed.
Location or variety of PokeStops makes no difference on how or when trainers could get a Dragon Scale. Despite Horsea and Sedra being water-types, PokeStops near bodies of water do not have a more significant chance of dropping certain items.
The only way to get one is to go out on your next adventure.