I've had luck using the Tech21 Midimouse (on my MophoX4), it's super basic midi out only but is pretty fool proof and lasts a long time on a 9 volt. Communication is one direction if you change a patch at the synth it won't update on the footswitch and the next change will be relative to your last patch number at the footswitch. It also can't change banks but if you put everything in order you should be able to at least patch up and down. There are some more complex (one control or Disaster area) options out there but I've never tried any.
Cheers,
Chris