I had the same problem with my switch. Nothing worked unless i pushed down hard on the rocker switch. So I took the dome assembly down and pryed off the rocker switch. Be careful when you do this. You will notice 3 spring loaded contacts. Those are the things causing the problem. You need to stuff something down the holes to prop up the springs again. That should fix it.

If its the plastic rocker that broke-i have a quick Mickey fix. You will see under the rocker is a little round hole-a screw set through a hole in the rocker will self tap right into that hole. Centerd in the rocker--the screw will-when loosened --allow it to be placed in diff positions(as if one really need such!) Tighten the screw up after setting it to a diff position. Getting the hole through the rocker is the most talent required-i didnt even bother to dig out a drill--just heated a paper clip on the stove and pushed it through. A nice little screw doesnt look that bad there either. This is the type of fix volvo drivers need to look for to keep their bricks affordable.

The switch is not available seperately. The whle light assembly must be replaced. Use a small screwdriver and pry the light lenses off from the rear side, revealing 2 small screws. Remove these screws and the light comes out.

I've never had to replace it, but when I intsalled my hands free cellphone I ran the microphone wire up under the panel where the switch is. That whole plastic thing with the dome lights pulls right down. Just gently pull at the front of it. It's only held in with clips. I don't know if you have to buy the whole kit and kaboodle or not, but it's easy to get too and an easy do it yourself job just from having seen it. Why don't you get one from a junkyard?