Well, typically the machine would have had a power supply like the second one you posted and the monitor power cord would have just plugged in to the three pin molex connector on it.
But you don't need that whole power supply just to power the monitor. All you need to do is adapt a standard power cord to it like you would plug into your wall. (say from an old PC power cord or something) Half a dozen ways to do it, just depends on your skill level, etc.