Not sure if you need to have a feature fabric with those colors all together in one fabric. If not, I've been to my LQS & was able to get all of those colors in Robert Kaufman fabrics. Sounds super cute!
Also, if you don't mind also having a bit of orange added to those colors, I got a really cute line from V.I.P Fabrics that has rabbits, carrots, etc in it with a pale yellow, grass green, bright orange, white & brown. It would look nice in either a girl's or boy's room. The line is called "Bunnies by the Bay".