These large, long, high-visibility drop cords are available on Amazon as well as many of the local big-box
hardware stores. They come in high visibility green, blue, and pink, and include a power indicator in the
clear female receptacle end. The wire is 12 gauge, which should be good for most loads under 15 amps.
I have also considered using this drop cord as a transmission line to bring my solar power to the controller,
since it's durable, rated for higher voltage, has a fairly thick all-copper conductor, and is high visibility.
And today I picked up a deal you probably won't be able to get but I just had to share. 100ft of 12/3 heavy
duty drop cord at Menards, on close-out for $39.99, and during their "15% bag sale", making it $34. Heck, the
scrap copper value is about that for this heavy cord. Didn't really need it, but couldn't turn it down.
("Performax" is Menards' electrical store-brand, like "ToolShop" is their hand tools store-brand)
I found a different generic heavy duty cord for a bit more on Amazon.