You can buy this at any good chemist’s, or simply make your own.
Once you have imbibed your fire portion, you must become big. Double in size. Go on.
Be like a contented cat. Or a fat pigeon.
Now, get wings. A wide choice of material is at your disposal in this modern age.
Remember: If you are big enough nobody will question if you actually can fly or not.
Your dragonly nature is now assured.
(Either that, or you’re in hospital.)