Those Pomona 2391 and 2401 BNC boxes are real time-savers, but can get expensive, especially if you need a lot of them.
I instead use the far cheaper Pomona 3754 and 2428 boxes, which I then top with PCBs with right-angle BNCs, like this:
That's the 3754 on the left, for two-port circuits, and the 2428 on the right, for 3- or 4-port circuits.
In the foreground is the underside of the PCBs. By cutting the traces with an X-Acto knife, you can solder through-hole or surface-mount components in series or parallel.
Here are the Altium source files for the 2-port box:
and the Gerbers:
And here are the Altium source files for the 3- or 4-port box:
and the Gerbers: