You could always get him a voucher for a sports shop, or if he likes computer games buy him one for GAME (the shop).
My neices and nephews have stack loads of things at home so I always end up getting them pratical things or giving them money with something small!
My nephew though, enjoys getting GAME vouchers because when he goes shopping he gets whatever he wants! In fact he has more money than me some weeks!
You could always get him a top or something, if he is into his clothes!