Well, I've come across a fanfiction named 'Inseparable'. In this story, Chris and Aviva are depicted as being truly inseparable, not just in their adventures but also in their personal growth. The author does a great job of showing how they support each other through difficult times. There's also a fanfiction that focuses on their backstories and how those past experiences shape their present relationship, called 'Origins of a Bond'.
There are quite a few Chris and Aviva fanfictions out there. For example, 'The Unseen Bond' shows how their relationship evolves over time, starting from just being friends on an adventure to something more meaningful. It's full of emotional moments and interesting plot twists. Also, 'Moments in the Sun' is a fanfiction that highlights their lighter moments, like their humorous exchanges and the fun they have during their escapades.