1999 Chevy Suburban Power Steering is leaking fluid like no

5.7L 1999 Chevy Suburban with 155,000 miles. Power steering works fines when the fluid level stays full but the problem is I have to add new fluid at least once a week. There is an obvious leak as evident by the large spot in the driveway and all of the fluid under the hood. I have used the "stop leak" fluid to no avail. It is obvious something has to be replaced whether it is the actual pump or rubber gaskets inside the pump. Can a power steering unit be re-built or do you have to replace the entire thing? I'm talking about getting it rebuilt or replacing... am I even on the mark?

Thanks,
Dennis