Pivot lock shoe replacement.

I'm afraid the cam is not available by itself. In fact, you won't be able to replace this shoe, either. Yours has a deep groove in the stem, which tells me that this is from an older model balance no longer made. You would need an all new Series 795 channel balance. You would then have to swap the bottom shoe out with our 15-194. The shoe that comes with the Series 795 would be too wide, but the 15-194 should be the same width.