How can a PC become more draconic?

Long story short, the frail, ancient 7th lvl wizard in the party I DM is actually a dragon who is slowly remembering his past and the dragon council’s curse that turned him into a human. He has learned his lesson over the years, and will be allowed to become a dragon once more when he is level 17 and can cast True Polymorph.

However, he wants there to be a sort of transition between what he is now and the adult dragon he will be able to become.

In the core rules (MM, DMG, and PH), what options are there to make a wizard PC seem more draconic or have dragon-like abilities? I’m especially looking for things between 7th and 17th level. Items, spells, and potions are all viable. I am a DM that allows UA, pending my approval.

For reasons of his own, the PC does not really want to multiclass, though we have discussed it as an option.

We are far enough in the campaign for the PCs to be known throughout the local kingdom and mildly inconvenience one of 3 major villians who are competing for power. They have a long way to go before saving the world, though.

I’m not worried about him stealing the spotlight, for the record.