Extension cords

Some folks have aquired extension cords at Home Depot and modified them to use as powercords.
So search the forums for the posting and get the extension cords. Go for at least 14 ga wires.

If you don't mind a little DIY, HD has 10 AWG twisted, stranded (for EMI, RFI rejection) Carol cord in bulk. They also carry some excellent male/female AC plugs that are very easy to wire (they're yellow, can't remember the brand.)

Signal Cable will make you an extension cord or a long standard power cord. I purchased a 3m standard cable which powered a ps audio passive filter (what is the name of the damn thing?) for something like 70 bucks; still have it and no longer use it.

I am sure an extension cable can be made if that is what you wish. The longer the run makes me want a higher quality cable/insulation; makes me feel better.

Another DIY option would be to start with a Hubbell 4 Plex outlet mounted in the matching box with your choice of plug and cable at whatever length you need. Like this:
Hubbell 4 Plex