You might also try posting a message to your alumni on your Web site, telling them you miss them and are looking for your chapter's alumnae sisters! You'd be surprised how many people do web searches and find chapters that way.
Also, you could ask them to supply their e-mail addresses if they want to hear about chapter news. Then send a monthly sort of "e-newsletter," especially designed to keep the alumnae informed about the active chapter.
Sus has great ideas for finding the alums. You'd be surprised, once you find a few and tell them who you are "missing," how fast they can help find other sisters. It seems like everyone knows a few different people's addresses.
p.s. have you checked the latest National Alumni Association Directory for any graduates of Nu?