pokeplushies.com is like dragonadopters but better my username on there is fab lampard
Try dragcave. Its addicting and more realistic than dragon adopters. You have a scroll, and collect eggs that need clicks/views to survive. If you take care of them, the eggs hatch, and if you take care of the hatchies they will grow up.
Chat with our AI personalities
Seadra is not a dragon type pokemon (it's just water), however its evolution Kingrda is part dragon. You can evolve Seadra by trading it to another game while it is holding a dragonscale. or in pokemon Black and White you can catch wild kingdra by fishing in rippling water (though it is very rare.)
If you mean just a normal one, you can get it from Duke Horacio during the quest Dragon Slayer or you can buy one off of another player or from the Grand Exchange.
You can make these yourself providing you have the materials and crafting level, otherwise you can do level 3 clues to get black dragon-hide pieces or you can just buy the set off another player or at the Grand Exchange.
Get a team of adventurers and just kill that dragon.
Just raise the power of Dragon type attacks.