This piece is used to transfer the RF signal from the circuit board to the C02 laser tube.

 

That is a banana post that was either mounted directly on a chassis or installed with an insulated chassis mount. Pomona is a big name in this type of connector. Many distributors carry their parts.

https://www.pomonaelectronics.com/products/banana-plugs-jacks-and-hardware/banana-plugs-and-jacks



ak

 

Indeed. That is a banana plug. But that one has a longer threaded stud and may be difficult to find.