I am sure if the folks at Home Depot said it can't be done, well then they must be right. Guess I'll go back and change the gazillion floodlights I relamped in my years as a lineman/electrician and change out the light that's illuminated my driveway the last 8 or 10 years.
Actually, a General Electric representative said we could do this (we're talking back about 20 years or so) as the locomotive crews complained about merc and metal halide brightness in the train yards where I worked.
Just to be sure, I went out and dug (can't believe I still have all this stuff in my shed!!) out a new 175 mercury vapor pole mount fixture and put a GE Lucalox LUH150/EZ lamp (high pressure sodium lamp) in it. I currently have the most highly illumintated bench vise in 13 Western states. E-mail your shipping address to me and I'll send you a lamp no charge. (If in fact your fixture is a 175 watt mercury vapor. Metal halide is a different story). h pressure sodium, by the way is typically the lighting you see on the streets/ freeway...kind of a brownish yellow. Low pressure sodium is the more buglight yellow.
ps; Just went back out to double check and my vise is still well lit. Luck, Kizmet