I agree with the other Gamma Phi, that the University's Alumni Association often has more accurate addresses than the international fraternal orgs. However, schools vary on whether they classify alumni by greek organization. I would imagine, though, that a Texas school would have done that by now. For more recent grads, just try facebook. They may not have a ton of cash to donate, but they may still feel connected to the chapter and help out in person. Good luck, updating info is a long, thankless task