Do these drop in the beta? I've never seen one, even in the shop.
Converse with fellow players
In the japanese version, they drop from level 76+ boss-type enemies in AQs/etc. (Beach Chrome Dragon, etc.) They might not exist yet in our version as a result.
Supposedly they drop from regular Chrome Dragon for NA, according to some reports. And also, on JP their main source is lv71+ Odin, the FF14 collab boss. Otherwise they drop from a special title Chrome Dragon during a certain seasonal EQ, which I think was the rainy one, and some collection sheets.