Digikey, Mouser, Future Electronics, Newark, and Hirose are vendors of the 50-pin mating connector for Tau2. The table below shows information extracted from a bill of materials (BOM):

DESCRIPTION FOOTPRINT VALUE SUPPLIER REFDES MANUF MANUF_PN CONN,50-POS, HEADER,HIROSE HIROSE_DF12-50DP DF12(5.0)-50DP-0.5V(86) DIGIKEY J1 HIROSE DF12(5.0)-50DP-0.5V(86)

Follow this link to Digikey where the mating connector can be purchased.