The part number is 204498, and they're about forty dollars when you find them, but when they quit working it's almost always a burned contact that's causing the problem. Since they open up with relative ease, try cleaning the contacts rather than replacing the switch. That's often all they're going to need to get them working again. The four claw like devices on either side of the metal closeout plate can be carefully pried back, then the entire plate along with the buttons will simply lift off. Once it's removed you have easy access to the contacts for cleaning.(white arrows) When it's time to reassemble the switch, pull all of the buttons up into their extended positions. A dimple on the metal tabs(red arrow) will drop into a hole in the buttons metal tang and hold them there making reassembly easy.

The way this switch works is simple. Three long and thin phenolic plates are nestled down into a pocket in the Bakelite housing seen in the photo below(yellow arrows). These plates have unique profiles on their upper edges that serve as cams. When you push a button to select any setting, the rounded end of that button's metal tang(blue arrows) pushes into its corresponding pocket and causes these phenolic plates to slide out of the way. As they move, the raised cams on these moving  phenolic plates then open or close the appropriate contacts. They're almost fool proof. In truth, I recently a purchased one of these switches to keep as a spare, and now I wonder if I'll ever actually need it. I should also mention that the temperature switch is the same type, so the comments above would apply to it as well.