Is there something he's really been wanting, but hasn't bought for himself? What about a get away somewhere like an overnight trip to B&B for himself and someone special. Is he into anything like fishing where you could get him a special fishing reel? What about tickets to a sports game he likes/favorite team? Does he like clothes? Maybe a cool leather jacket? A watch or piece of jewelry he could keep and remember you and his special occasion by? A season of DVD's of his favorite TV show? Take him to lunch or dinner to celebrate with you and praise him on his efforts, ordering a birthday cake for him?
Congrats to him! Thats an amazing accomplishment.