Shop/Garage Heater suggestions please

When I'm under the car, I work on a sheet of styrofoam,They come in R5 and R7 per inch. I find a product called SM-Blue at 1.5 inches very comfortable even at down to 55*F. They come in 4x8 sheets. They are fairly robust too in this HiDensity material. I drag a partial sheet around, almost everywhere I go. Years ago I built a modest wood frame , about 8ft hi in a rectangle around the car, and draped a large sheet of plastic over it.Then a portable Kerosene camp-type stove under it. That was very cozy. The tools however were always cold,lol.