Check Lifeway Book store or the Family Chrisian Book store for their little baby bibles. Have his name put on the outside cover and on the inside write down his info and the date of his baptism. That will suffice. If it's blue, he can read from it on his wedding day. If its white, he can give it to his bride to carry with her bouquet :-)
Keep it simple. Simple things are sometimes the best things to give. If the godparents give him this as a gift, even better. At this age he doesn't need anything, just you continuing to see that he receives his Christian education. That's the best gift that will last forever. Otherwise just take lots of pictures