It's tough because I find stuff that says it's sold by Big Hit, and then you click it and it just takes you to a search page, not a company page. But I assume this is official: https://www.amazon.com/TXT-Chapter-Eternity-Photocards-Starboard/dp/B087TMQVNW/ref=sr_1_45?dchild=1&keywords=Bighit&qid=1589229253&sr=8-45
Personally, I'll be buying the digital album off Amazon, and I don't think there's anyway for that to be sold by a third-party.