Rhodes Chroma Polaris

Does anyone know of a suitable footpedal that will work for this . I 
tried a Roland ev-5 expression pedal, and it wasnt apparently very 
effective. (did a little modulation change but not what function it was 
selected to do).  It seems that other footswitches do well for the 
sustain function, and metronome,  but the assignable control needs 
something special.