Well, I'd try a doing an online search on amazon or another site and reading reviews to find books most appropriate for your situation, but a few to get you started (and don't forget to check the "see more like this" lists if you look them up):
Standing on my own two feet: a child's affirmation of love in the midst of divorce, by Tamara Schmitz
The best of both nests, written by Jane Clarke; illustrated by Anne Kennedy
Priscilla Twice, by Judith Caseley
Dinosaurs Divorce by Marc Brown
Was it the Chocolate Pudding? by Sandra Levins