I don't believe it's possible for any reasonably simple analog circuit to phase-shift all frequencies equally. Any usual phase-shift circuit will use reactive components to do the shifting, and that means the phase shift varies with frequency.
In theory it might be possible to do a series of Fourier analyzes of the signal, shift the phase of each component and then regenerate the signal, but I suspect that would take a large amount of processing power to do in real-time.
And what results do you expect from doing this phase shift?