[BlackAura]

The word you're after is "agender". So, pretty close.

The answer is - whatever they tell you to. Some would prefer "they". Others wouldn't care if you use "him" or "her". Yet others prefer some invented pronoun (there's a long list).

The only one that's likely to be inappropriate is "it". Don't use that.

[sugerman]

I reserve "it" for unborn babies whose parents don't know the gender.