The simplest way (and the most accurate given your disco ball analogy) is to have that object reflect a much larger sphere that has a texture loaded in the luma channel. Add a compositing tag to the sphere and turn off the "seen by camera" button. As the camera moves or the object rotates, the facets will catch different parts of the scene. If you make this a separate pass and then composite with a glow effect, its very convincing.
If the ball doesn't reflect enough facets and looks more smooth, you can remove the phong tag on it or change the phone angle to a smaller number so that facets show instead of being smoothed.
The texture loaded on the sphere can be as simple as a few big soft white circles of different sizes on black. Need more sparkles? Tile the texture more on the sphere.