(More for others who might wonder the same thing than the original poster who is unlikely to still be around).
The greeknet link above is now invalid. Assuming you are looking for a professional fraternity i.e geared toward a particular profession/major as opposed to a social fraternity, in terms of Professional co-ed fraternities, they'll normally be a member of the PFA (Professional Fraternity Association, Inc.)
http://www.profraternity.org
Just like many male (inter)national social fraternities are members of the NIC. If you look at the PFA site there will be business fraternities there.
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