[knight_shadow]

Pardon the crash, but I wanted to throw a few ideas your way.

Do you have contact information for any alums? In my organization, the alumni members may not keep in constant contact with collegians, but they do keep in touch with each other. See if the alumni members that you do have contact information for keep in touch with others (ask them for, say, their pledge brothers' information).

Does your alumni chapter maintain a membership database? You may be able to get some information there.

You may consider hosting some kind of alumni appreciation dinner or barbecue. With some of the organizations I've come in contact with (including my own), older members will come around if they have a reason to.

Hope this helps. I'm sure your brothers will chime in with additional responses.