Tom,
I think others have suggested pvc, and that would be my first choice also.
Drill 2 holes at one end and attach to the tower leg with a u bolt, or
invent some other attachment depending on what you have laying around. Cut
a slot into the other end so the slot will be vertical when the standoff
is attached to the tower. Spread the slit open and slide in the ladder
line and it will grip it tight.
Have fun with the new rig.
73, Steve KW3A