I agree with jewerly. A cross pendent would be nice. If you google baptismal gifts you should be able to fine lots of items.
Also when my nephew was christened his godfather(who is also his uncle, I am his godmother) gave a picture frame, on one side it holds a picture and on the other side it is engraved with date, names of the baby, parents and godparents and a beautiful poem to remember the day by. My sister has it in his room with a picture of him with his parents and his god parents.
Jenn