The Benchmade rescue hook is available with a molded plastic sheath which can be attached to the helmet with cable ties. You can do the same on the speader bar.
http://www.benchmade.com/products/pr...l.aspx?model=5
When I was using this knife, the sheath was attached to my spreader bar with cable ties and I had a length of nylon cord tied to the knife in case I ever dropped it.