Hi Bob,
Have a back support belt? If so, simply put an "S" hook on each end of a 36" piece of chain. One end attaches to the buckle of your belt. The other end loops through a plate and hooks back into the chain. If you don't have that type belt, any wide webbing material (to spread the weight across your lower back) will work just fine. Perhaps a rappelling harness is in your arsenal?
Good luck.
Arcturus