Joe, I got the part from MIE Maserati parts, a reproduction that also necessitates changing the outer tie rod, fits my Longchamp with ZF steering and Quattroporte III. It cost $333, very very expensive, but I guess we have to be grateful that somebody still bothers to reproduce these things to keep our cars running. Try contacting them.
If not, Roger Brotton in the UK is parting out a Longchamp, but that will be a worn part obviously.