Oceanic has had a lime green and blue together but not now. I have seen green mask, fins and snorkel in the past but haven’t been shopping recently for gear. Neon Yellow looks green underwater :) Much of my daughters gear is green.
At one time Deep Sea Supply did custom colors for their wings. One of the women on DB has a purple one and is/was a dealer for DSS so WreckWench might be able to help you. Starting a growing kid out with a Back Plate & Wing would be a smart move. As she grows you just leave out more strap and move the D-rings plus the harness is weight belt material and that can be found in green :)