Just a couple of thoughts: (1) Would you consider a tablet (such as an android device) with an app that can do sysex via Wi-Fi? (2) Would you consider building your own sysex sending controller with a low-cost micro processor, say something like a arduino or a pi--or maybe modifying/adding on to something like an old ART? foot controller? (3) I recall reading about one (other that the BCF/BCR 2000s), but will have to look for the reference--I think I might know someone with a programmable foot pedal.
Steve