There is no “ other vendor” for a direct replacement for your MTH Niagara, ….plus I doubt you’ll ever see that exact tether produced ever again ……beings your tether is still good, and just your outer jacket broke, I’d use this harness I have pictured here, and splice in the tail end that you need,….this is pretty much a universal repair tether. All you have to do is match color for color and go,…..naturally, double check your work with a DVM/multimeter…….
Pat 
