Reverse sweep modulation

Hi all. I'm looking for something I am not sure exists. I want to take stereo tracks and apply modulation that sounds like it's going opposite directions. I am wanting something "flanger ish" doesnt have to be a flanger. Could be a panning type sweep or resonance of some kind. Just want the kind of sweeping movement modulation but are there any that sound like the sweep goes opposite directions. Eg one up one down (or however you perceive it).

Physical pedal is preference/plug ins are all good if it is somethingthat need to be achieved in post. Just need to find a solution.

Thank you