Where can I buy dragon scales? I completed the main quest line, so I don't think I'll be seeing anymore dragons, but I wanted to make some nice armor while finishing up the side quests.
No, no one sells them, but you will continue to encounter dragons after the main quest line so you won't run out of bones
Dragon Bones and Dragon Scales are not sold by any vendor.
After you've finished the main quest, the random dragon encounters still happen
and you can now call upon Odahviing to help you fight those dragons
You can still get Dragon Bones and Dragon Scales as well as Dragon Souls from those Dragons.
This'll allow you to create all the dragon armour you want, as well as unlocking all the available shouts.