A heavy duty 6 foot 120 Volt extension cord is expensive, so make your own for about $1.50 each.
Remove the heavy duty cord from an old appliance you are recycling.
Pass the end through one of the holes in a $0.39 blue single gang workbox.
Then tie a knot for strain relief.
Strip the ends and attach to a $0.59 15 Amp outlet - green wire to green screw, white to silver screw, black to gold.
Screw the outlet in place and add a two outlet nylon "unbreakable" cover plate for $0.47 and you are done.
Plug and play. Remember extension cords are for temporary use only in dry areas.