The best expression pedal is one that works...
I learned that lesson the hard way, first buying a pedal for my PSR that the salesman at "The Evil Empire" swore would work... They took it back, but didn't have the correct unit available, I ordered one directly from Yanaha. Check the pedal out in the store, connected to an instrument like yours, if they don't have your instrument in stock, bring yours and set it up... It may just save you an unneccesary trip.