Came across this method the other day - you need to have a outdoor gas ring or a very co-operative partner and/or well ventilated kitchen :)
Put some coals on a wire rack over the flame
After 5 mins they look like this
Pop them in a tray with others
I normally give them a blast with a hair dryer to get them going
After only 30 mins smoker is already at 120 c
Worth a try....