Normalizing using RMS as opposed to Peaks.

is it possible to get a Plugin or something to use within Audacity which can handle RMS Normalizing?

Fair warning RMS Normalize is not a “get out of jail card.” It will respond to rumble and microphone data errors you can’t hear and may create overload and clipping distortion. That’s why it’s used in the middle of a correction suite of tools and not by itself.