There are no plans to have double rewards for winning battles. Unfortunately, the only way to get your Gladiator Dragon is to buy the remaining Morningstars with Gold in the Spell Shop. I have mentioned to the team that sending out some sort of warning before we're about to change the reward would be helpful for you all, if we change it again in the future. This would allow everyone a chance to get in their last battles if needed. Good luck with this new Dragon!