propane hand held torch that attaches to a bbq tanks and a dolly to put the tank on.
harborfreight has them for $20.
Walk the driveway after a rain, or when there is dew and singe all of the plants to the ground.
I had a friend who made a potential boom squish attachment out of a small, hand pump sprayer something like this
and copper pipe wound around the flame portion, it had pressure release valves, so no boom squish. it shot steam out so fire hazard was low.
it made good steam without having to pull the trigger on the porpane torch. that is, just the pilot light on the torch was enough to get good steam.
It's been a while, but I think we attached the wands together with zip ties and used the trigger on the sprayer for steam production.
not sure if that makes sense, it would require some tinkering, and careful planning to avoid death.
However, we used it and it worked great.