[Teddy]

...In South America, where I write from, it's not easy to find an endocrinologist with ample knowledge on phytoestrogens and herbs, she wants me to gather the information and consult with her before deciding what and what not to take. ...

Hi Yaraé, and welcome!

I can understand your frustrations with customs and finding "unusual" supplements. However, often less is more, and you might try some easier available substances first. In m.h.o. Pueraria Morifica is the most powerful herb for feminization and breast development. but it is likely difficult to find locally. And importing  could be problematic, too. However, Fenugreek, which is a common spice in many cuisines, might be easier available. Please read about it (Lotus has collected a lot of herbal information an scientific articles). Another thing you should consider is a testosterone blocker. Reishi mushroom powder might be available locally. Or maybe not as powerful, but still useful Saw Palmetto, which is used by many for instance against prostate problems.

Additional useful supplements, such as MSM, Vitamin C, Calcium/Zinc/Magnesium supplement, might be likely also locally available.

In your situation I would first look a bit deeper what the more experienced people, such as Lotus, have written, and then do some internet search and visits to shops selling supplements. Then you can find out what is feasible when in Columbia.

_Teddy