Silverdome urinals for sale, but don’t ask Barry Sanders to sign one

What do you get for the Lions fan who has everything? If he’s already got the Lions’ terrible 2013 calendar or a shirt commemorating their undefeated 2008 preseason, you could buy him a Silverdome urinal. Yes, the owners of the Pontiac Silverdome, the once state-of-the-art stadium that has been largely vacant since the Lions moved…