The Instruction Ut sive of 1969 removes them (n. 19). Mind you, I’ve regularly seen cases where Ut sive and following instructions are flouted. Or at least, appears to be flouted, though those concerned may have renewed privileges or holding onto them. I haven’t seen any canons wearing the grey mozettas with violet piping prescribed.
Without casting doubts on the stores, there *are *only a limited number of bishops in the world. And from my meager experience, not many are concerned with wearing purple socks. Also, as lak’s post mentioned above, after Ut sive, a chaplain to his Holiness is no longer entitled to the purple cassock choir dress, but a purple trimmed black one, with a purple sash.