I realize TAZ is thinking more along the lines of just who is showing up, but since we have some dedicated members that just plain can't come, does it have to say something about this particular trip? How about keep it simple and just have «BuA» embroidered on the front or back? Of course, an embroidered hat is probably going to cost a lot, but a simple hat like that we can keep around to give to other members or replace old worn out ones, so getting a dozen wouldn't be a bad idea.
If we are going to do something Lan specific, I'd say a t-shirt, because those would be cheaper and quality wouldn't have to mean quite so much.