What about rush shirts?
Maybe fraternities don't do this anymore, but back in the day...fraternities used to have rush shirts. (Rush XYZ, or some more clever slogan, etc.) It was quite common for female friends or girlfriends to be given these shirts. (Of course, it was generally the very attractive female friends or girlfriends who were given these shirts...I always assumed it was a form of advertising.
As if it was implied that by rushing XYZ, you'd be hanging out with a bunch of hot babes.)