PCB Connector for Sensitive ADC Component
There are a huge amount of choices for this I would think.  Maybe a Qstrip similar to a mictor connector


It has a nice ground/reference plane in the middle and you can space the signals out from one another by using a connector with more pins than you need.  Maybe isolate around them with some GNDs and you should be okay.

Or I just used something like this, it's a high isolation RF connector