In Canada, we have a supplier called Princess Auto that has lots of solar stuff. Also, what I have done in the past is forego the extension cords (definitely a headache and very dangerous) and purchased heavy cable, say 10 guage, put my own male and female plug ends on it and made my own extension cord the length I needed it. If you go this route, the heavier the cable, the less voltage drop you will have. BTW, I also fed the cable through some 1/2" poly piping to protect it from horses and equipment. Then I buried it about a foot into the ground, just by hand digging. Easy enough to do, just time consuming.