You seem to mean this connector. Unfortunately, this looks like a proprietary HP/Agilent/Keysight design. Apart from the expensive connector that appears as a spare part from Keysight, no one seems to make it. The application I know is the 85024A high impedance 3 GHz probe (plug). I have sockets in HP, R&S and Anritsu devices. There is no manufacturer number or mark on the plug.