birthday gift ideas for a transformers fan?

my bf is turning the big 21 in a few months and he absolutely loves transformers. quote “I don’t know who I would be without transformers”. i really want to surprise him with a memorable gift that speaks to his inner child since 21 is like adult adult not teenage adult. what are some gift ideas that are on the affordable range but very memorable? i did minecraft theme last year for his birthday, so going on a streak. he is not a figurine collector so i feel like that widens the options.