I wear a 30E bra and Women's 8 fits snugly - I like a snug fit, maybe you don't. I tend to find that Men's Small is very baggy, which I don't really like in a technical Tshirt (but maybe you do); I'd expect children's sizes to be insufficient in the bust area.

You are welcome to try mine... if I manage to be in the same place as both you and it.