There is, or at least was until recently, an airline memorabilia store at ORD that had an incredible selection of that sort of thing: Eastern Airlines golf shirts, what have you. Go through the tunnel from Terminal 3 (AA) toward the O'Hare Hilton. Pass the transit connection. It's on your right, exactly opposite where you'd turn left for the hotel.

Perhaps someone else can confirm that it's still in business or provide a name so you can call. Or, if you have a longish layover there soon, head on over - to most FTers it's fascinating.