How about a personalized poetry book written just for him? You could collect his favorite poems from the various slams he's attended and compile them into a book for him to cherish. You could also consider hiring a local poet who specializes in performing original pieces to create a piece specifically for him, which you could then include in the book. Additionally, you could consider booking tickets for the two of you to attend a poetry slam together as a special anniversary date.
Or you can get him a star map with the date of your anniversary.
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.