I would try leather staps. Maybe two belts at first. You can go to a sporting good store and get the straps. I would NOT use bands or tubing. Now I only say this b/c I truly care for my fellow Catheites, but when I read that my mind screamed "DANGER WILL ROBINSON! DANGER!"
The towel idea would work.
I just wouldn't want you to fall on your tooshy and not be able to workout for a week. That would be a MAJOR tragidy!
Just MHO and .02
~Reece Out~