Here is the template for you to build your own footrest to set down over a Logitech Marble Mouse trackball as demonstrated on YouTube.
You can easily adapt the design to fit any other kind of trackball.
If you can’t build the foot rest yourself, any handyman can do it for you easily. It should take only an hour, not counting any time spent buying the materials. I do not make and sell them myself. You are free to use this design any way you like, as long as you do not profit financially from it.
Please let me know how it works out for you.