Although you broke up, you are still ordinary friends. It's good to send birthday gifts to express your blessings.
Does he have a girlfriend now? If so, don't let others misunderstand. If not, don't be too rigid about the gift. Give him chocolates. You can DIY blessings. It's very suitable for male friends.
Or you can give him a cartoon doll, made with his photo, and matched with a cute scene base. It has a warm feeling and can better reflect friendship and blessings. It's quite suitable.
Don't consider giving lighters, ties, wallets, etc. as usual for boyfriends, so as not to cause other misunderstandings. If you really can't decide what to give, I think sending your blessings is the best. After all, you have broken up. Between ordinary friends, blessings are the most simple and direct.