Yes the Midi Solutions Footswitch Controller WILL work for you.
You will need an on/off pedal. Something like this:
Plug the 1/4" into the Midi Solutions Footswitch Controller. Then connect the Midi Solutions Footswitch Controller to your sound module with a MIDI cable.
If your controller is really old, it probably does NOT transmit "MIDI velocity". In other words, there will be no dynamics sent from the keyboard if you play the keys hard or soft - it'll all be the same, which really does not work for piano playing..
You might be better served getting something like this, that transmits velocity and you can connect a sustain pedal directly:
M-Audio Keystation 61 New about $200, used a lot less.