Celt -- ROTFLMAO!!
Seriously, Hongkong2 does it the way I've always done it. Some restrooms have their paper in a rectangular box that is enough of a shelf that I can set it there. Otherwise, your pants are at your knees and you set it in your pants, between your knees. If you don't use a paddle holster though, the other concern is someone seeing your holster on your belt. For that, some artful draping of the folds usually solves the problem.
As for the urinal situation, this was once posed as a question in tactics, I think on the Glocktalk board. My response when acosted while using the urinal is to immediately turn around and piss on his leg. His shock should disrupt his plan enough for me to simultaneously draw my handgun and more permanently solve the problem. That is, if the mere sight of my major caliber unit doesn't cause him to flee before I can shoot him.