I want my son to understand that he can wear, do, or play with anything he wants

I have a four-year-old son, and his father is very "that's for boys and this is for girls," and "you can't wear/do/play with that because you're a BOY."

My hope is that this beautiful community of families can help me by suggesting books, movies, or other resources that might help us get the point across to our son. I have looked high and low and I've nabbed the materials that I feel express my feelings, but I want as many tools as I can to help my son understand that he can wear, do, or play with anything he wants.