Does he have a basketball hoop? If it’s something adjustable/sturdy it’s nice because he can use it for a long time, even as he’s growing.

Jersey or shirt with his favorite team

This kiddie basketball arcade game (there’s other ones in a similar price range, so you can pick the best one for him): Kiddie Play Toy Basketball Hoop Arcade Game Indoor Sports Toys for Kids https://www.amazon.com/dp/B07DM5LBK5/ref=cm_sw_r_cp_api_i_2H921C6BAMYR45GT3HGD

A customized blanket (this website has lots of different options, I just searched basketball and found this. There’s plenty of non-basketball options too. Also, I have ordered a lot from this site over the years so it is safe and pretty good quality too!): https://www.personalizationmall.com/Basketball-Personalized-50x60-Plush-Fleece-Blanket-i90980.item?productid=33459&sdest=Search&sdestid=129314914