If you just need a temp. 50 amp hook up, and not a permanat installation, I would suggest calling a equipment rental company. Ask for a 50 amp cord, 50 feet or more, and a 50 amp pig tail, if they have it. Then just purchase the 50 amp outlet. Call a Licensed electrician and have him do the temp install. Or just ask the Electrical contractor if he has the cord and equip. and rent for the time . Shoud be much cheaper than a permanant install w/ permits, trenching, etc.