Welcome to our forum.
There's a couple of external links you could try:
But you are right, it would be difficult to find a list of people in Argentina.
If a counselor is really good, don't rule them out; they might be willing to study up on polyamory, and be accepting of your orientation/situation.
You may find that interactions on these boards are helpful too. But it is good that you are also seeking a professional.
Glad to have you with us.