dpete, are you talking about those really big 1000W work lights that you get at hardware stores?
i use one of those for fill sometimes, and the only thing that really works is going to a film store and by some diffusion like a frost, a grid silk. stuff like that. they're made to withstand very hot, concentrated light, since most of the time you just clip it to the barndoors on fresnel lights.
you can also get frames that you can stretch the diffusion over, and that way move it as close or as far as you want from the light.
i don't know where you live, so you may or may not have a place that sells film supplies.
and they sell chinese lanterns at Ikea in all different sizes and shapes too. they change the light around in different ways. do you have an Ikea near you?