Go on the mitsubishiparts.net website. Find the number and call them up. Thats how I got the part number. Heads up, its $90.

I think thats a bit pricey, so I fixed mine. For me the arms inside the switch cracked, so I glued them on and then took two needles, heated them up till red, and stuck them through both pieces of the arms to melt the plastic and provide a support. I also removed the spring thing inside to take away from the switch tension preventing another break.