M., What a wonderful godmother you are that you are really thinking about something that will help you interact and get to know you godson better. That is really what it is all about isn't it?
I hear that you want to buy something with a religious based theme. I have worked with children for many years and the acquisition of faith and religion developmentally comes much later for children. It is abstract and they don't start having abstract thinking until they are 11 or 12 years old. You may think other children are very "religious" because they talk about religious issues but they are really repeating what their parents say but don't fully grasp it.
When you say that he is a loner it makes me think that it would be great for him to connect with you. I believe you do that by following a child's interest and becoming involved with them while they are doing it if they invite you. Perhaps you could ask him what he wants or ask his parents. Boys his age love Legos and their are great kits out there. I think the religous part comes in when a child forms a relationship with you and learns about caring, sharing
and seeing you enjoy his company. A.