If you don't have about $10 million, like the set auctioned recently here:
A Rare Copy of Audubon’s ‘Birds of America’ Heads to Auction to Benefit Conservation | Audubon
you can download and print all 435 yourself for free here:
https://www.audubon.org/birds-of-america
A Rare Copy of Audubon’s ‘Birds of America’ Heads to Auction to Benefit Conservation | Audubon
you can download and print all 435 yourself for free here:
https://www.audubon.org/birds-of-america