Jesus said "Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit." Matthew 28:19
Baptism represents the forgiveness and cleansing from sin that comes through faith in Jesus Christ. Baptism publicly acknowledges one's confession of faith and belief in the Jesus as Lord and Savior.
You are looking for a Baptism gift for your child but remember that Baptism is a gift in of itself. Baptism is the most significant ritual in the Christian faith and is a defining moment in the life of the baptized. People give baptism gifts to those who have become baptized to mark the occasion.
Baptism gifts for children are sometimes challenging. Bibles are common baptism gifts. But for kids age 3-9, you can get them a Talking Jesus Doll. It has the fun value of a toy and the spiritual value of reciting Jesus lessons from the Bible. It serves two purposes and is a great baptism gift for children.