Lowes has the Unistrut and the sliding nut, just a different brand. I am not sure if they have the 1 1/2" metal strapping.
It will take about 8' to do a tractor. I was going to just use the Unistrut for the horizontal, then verticals as a temporary until I got the height figured out, then build a  bracket to fasten the horizontal too, just to get a nicer look. I decided that the verticals would be a good addition to mount other things on and fasten the wires to.

JB59