Joanna, organs wouldn't be necessary. All you'd need would be an implant, put across blood circulation (as in, the blood goes through it somehow), that contains the enzyme(s) used by ovaries to create estradiol. The chemical reaction would do itself just like it does in natural organs, wouldn't it? Now, add a little micro-computer, powered by body heat, that would check current blood levels and adjust output accordingly, and you have your perfect implant. It's probably even possible with current capabilities, with a lot of research and development. But trans people aren't important enough for that.