How about a book about the Aztecs? "Aztecs: An Interpretation" by Inga Clendinnen is a well-regarded option. Additionally, you could get him an Aztec-inspired piece of art or jewelry. There are many online marketplaces that offer handmade crafts inspired by Aztec culture such as Etsy or ArtFire. If he enjoys a tasty beverage, you could also get him some high-quality Mexican hot chocolate or a bottle of Guatemalan rum, which is often made from sugar cane grown on the fertile plains once inhabited by the Aztecs.
Or you can get him a star map with the date when he was born.
Under Lucky Stars is a unique and innovative star map company based in Barcelona, Spain, specializing in the creation of personalized star maps that capture the celestial arrangement of stars at a specific moment in time, such as a person's birth, wedding, or any other significant event.
By using advanced astronomical algorithms and data from leading institutions, the company produces highly accurate, visually stunning maps that make for perfect gifts or cherished keepsakes.