FOUND: Metal dome (switch) for 701c mousebutton

[schnitzelcore]

Sorry for my bad english, I don't know the technical term for what I need.
Under the two mousebuttons of my 701c are two small 'metal domes': these are the actual switches. One of them has a crack in it. It still works, but the button has gone all soggy and lost it's 'click'.
Does anyone have a spare or know someone who sells this part? If you know the technical term, please reply so I can search for it!

Edit: Cannibalized a broken Tecra 8100: the domes were smaller and had to be surgically cut out of some plastic sheet, but seem to work. Bit lighter feel than the original, but 'clicky'.
Sorry for this, but maybe someone with the same problem can one day find this solution with the search () and as I replaced both domes I now have one original available...