Try doing a google search to find a website for the Alumnae Group (if the local Alum chapter has one)
Hopefully that will provide you to contact information for some women (like the officers for the alumnae association) to get in touch with so you can get the ball rolling on securing a rec.
you could try calling xyz headquarters and tell them what is going on and ask for the name of another person, perhaps and alumnae chapter president, to contact.
Also, try doing a search for the chapter's website. It will often list names of advisors and sometimes the names of women who hold alumnae offices in the area. From there, it should be a phonebook search.
Most areas of the country also have an allumnae panhellenic conference which may be able to help. Allumnae panhellenic groups should have at least one member of each major sorority (a delegate) who is usually a different person than the reference person for that particular chapter (at least in my alumnae chapter it is).