I'll chime in with another vote for Decent Exposures. These are the only bras I wear and have been for years now. My dd is 9 and has no need even for a training bra yet, but I have long thought that I would suggest Decent Exposures when she is ready. Right now they sell girls' sizes in 100% organic cotton in cream, white, pink, blue, navy, and black.
Here are their fabric and color charts