As previously suggested use a flashlight I shoot with a Canon and at times have the same problem.

I normally use one of the firefighters flashlight off the truck put it in the pocket of my bunker coat. The flashlight is angled so it faces forward and normally I can position my body or the flashlight so it shines on what I want to photograph. Get the focus holding the shutter half down and then you can turn your body away so the flashlight in your pocket does not shine one the scene you want to photograph and take the shot.

Other option is if you have someone available get them to hold the flashlight. Works well when you have to move to different rooms in a scene this way you do not need to move lights around.

Regards,

Kevin Gallant C.E.T., CFEI, CFII