The CDV-700 probe socket was epoxyed in place and the socket itself made of phenolic/bakelite. There is no simple/safe chemical that will dissolve either the epoxy or the socket without also destroying the chrome plated brass probe housing.
The easiest way to remove the old socket plug is to cut the cord flush, then soak the base in mineral spirits for a day.
Take the base out, shake the excess mineral spirits off and turn it upside down on concrete. Heat it with a hair dryer or heat gun until it begins to smoulder or the chrome begins just to discolor. The idea is to heat the whole thing slowly and uniformly so the brass will expand and separate from the plug inside.
Allow it to cool and insert needle nose pliers, twist and pull.
The socket base is a Cooper-Allied Interconnect 78-s3s
A suitable cable is M17/119 RG-174. This one is rated 1100V and is slightly under 3mm outside diameter.
Pin 1 is hot, 2 and 3 are the braided shield/ground. The yellow sleeve is heat shrink tubing. It shims the cable up to 4mm, the size of the hole in the base. I tie a knot just behind the back of the socket so if the cable is tugged hard it won't pull out the wires. A drop of Gorilla Glue on the socket before assembly keeps it in place. I don't pot the base with epoxy like it was orginally, that just makes it harder to repair if it needs to be.