Which computer power supplies produce clean power?

You aren't making any sense. A trifield device measures noise from the input and has nothing to do with the "produces clean power" which is about the output. Further, what does it matter? What is the application where you are forced to have sensitive equipment located nearby, that don't have their own suitable noise rejection circuitry as less than a volt of noise is a pretty low level in the bigger picture, where anything sensitive would be regulating to a more precise voltage anyway.

I'm just getting the impression that you don't understand that what you are obsessing about is not a problem. Without more details that describe a specific rare scenario where it is a problem.