I don't know how your machine cabinet is set up but I'm wondering if you can put a pool noodle or piece of lumber across the back. That would at least keep it from going underneath the back. If from side to side, one of the suggestions was a foam back bath mat or the like and put the pedal in a cut out section. There are some more suggestions in a couple of threads here on QB
traveling foot pedal and
Sewing machine foot pedal