Don... you might be able to get the same functionality you have with the PA1000.

A company called Midi Solutions makes a module called the Footswitch Controller. It can be programmed to send a MIDI message on initial press of the footswitch, and a different one upon release.

On another thread I posted about wanting "Bass Inversion" to be a MOMENTARY function, for those songs having one odd slash chord. (I didn't want to press a pedal once to turn it on, and again to turn it off in the middle of a song.) I got their Footswitch controller and was able to make it work just like I wanted. I'll bet you can do the same with your harmonizer volume. Just a thought.