look for ‘sci­ence’ dis­cov­ery type toys, like an ant farm, or sim­ple sci­ence experiements he can do like mak­ing a ‘vol­cano’ with sim­ple indre­di­ents.
Six year old boys often like bugs, maybe you could get him a book on bugs and a mag­ni­fy­ing glass?
They also like dinosaurs. Any books with lots of pic­tures and maybe plas­tic dinosaurs to play with. Or a dinosaur bone skele­ton puzzle.