I like the idea of purchasing gear versus fabricating it, for safety rated equipment.Noooo, dont do that. What you need to do is go to Eastern Woods Outdoors and buy stuff. Probably should get parts for 3 maybe 4 different setups to figure out what will work best for you and then list the other stuff on the classifieds.
The only thing I see on the EWO page is a Beal Air Step (Foot Loop), that would fit this application. If the foot loop is adjustable, but if it had wider belting, I think it would be ideal. Without calling EWO and asking the size of the loop, there's no way to know if it would fit over a particular boot style or size.
Also, I would prefer a wider belt size to avoid the same uncomfortable issue in the arch of your foot, of using a rope.
Perhaps there are other companies that offer belting, for such uses.