After asking the keepers at Emerald and looking for myself I have come to the conclusion that Emerald sadly only houses 2 males (possibly 1 since I spent almost an hour in the aviary today and couldn't see more, but they always find ways to hide).
I would love to see a female appear in the aviary, but since the keeper told me she believes they only have the 2 males (she is new at Emerald and started this year) I don't think it will happen.
This sadly means that Emerald will lose this magnificent and rare (in captivity) species if nothing is done to introduce more.