Well, I guess the appropriate question is
Whats leaking?
There are several different items associated with the standard PS.
Low pressure hose, easy fix,
HIgh pressure hose, easy fix
Hose connections, if not stripped easy fix
Power steering fluid reservior, could be an easy fix
Power steering pump or gear box, not easy to very difficult.
All that being said, I have never heard of any product that would stop a leak in its entirity as most of the PS system is under increased pressure
I dont think I have given any real help but maybe a couple things to look at and eleminate..........