Some years back there was a person that made the equivalent of the four pedal switch except it was comprised of four small button switches that mounted just outside of the keyboard on the left side so that all could be controlled easily with the left hand instead of the foot. The article contained complete directions for constructing such a device, including a schematic.
So far I have not been able to locate the article - maybe someone else can jump in here. If I do find it, I'll pass it on.
Walt