i would look on http://opposedforces.com/parts
some times there are slight differences that will give a certain part a different number. but that does not mean you cannot use it on a different car. in the late 90s, the GT had a few suspension parts that were different from the ''L'' model like the front sway bar, but not many. the struts, hub, knuckle, tie rod end, steering rack were all the same. i doubt the cross member is different.
but what ever you find, i would not buy new. i would buy from www.car-part.com
.when you search for the crossmember for the 97 GT the software on that site will return results from all the car / years that will fit your car. the software is pretty conservative and if there is any doubt it will not bring up the questionable year or model.
i believe the cross memeber in your car will fit any legacy / outback /GT /LSi / brighton, 95 - 99 .