As Bj suggested, stop in at your local HD or Lowes, pickup some heavy duty ext. cord. I recently picked up some 2 X 100ft and 2 X 50ft Rigid heavy duty ext. cords from my local HD, they aren't cheap but well worth the price.
As stated above, the longer the run, the heavier the cord will need to be. Check the packages, they'll show a chart.
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