Thanks for all of your responses. From what I can see none provide what I am after which is a proper surface connection for a simultaneous connection of a speaker cable terminated with a spade and a speaker cable terminated with a banana plug, or two speaker cables terminated with banana plugs, on the one banana plug. The suggestions all appear to be for a bare wire connection typically using 2 screws. I already have terminated speaker cables, not bare wire ones, which I wish to use. I do not propose to use the 2 screws to clamp down on the banana plug and in any event there is nothing offered for the second terminated speaker cable.
I have two old pairs of Monster Cable banana plugs circa 1990 where the black marked ones do not have a dialed back which rotates down and expends the banana plug once inserted in the speaker's binding post, but a female banana socket allowing for a good connection with a male banana plug, and on both the black & red banana plugs there is a middle section which unscrews and will accept a spade for a tight connection. I am guessing that this female banana socket just on the black marked plugs was for an earth connection. I wish I had bought 4 pairs so I could now make up the 2 pairs I need.
I am after something like these old Monster Cable banana plugs or a banana plug equivalent of the WBT or Furutech binding post which accepts both a spade & banana plug.
As to comments made on super-tweeters offering no improvement, which was not the subject of my question but which I gave as background as to how I wanted to use the banana plug, I have considerable experience with using 2 pairs of ENIGMAcoustics Sopraninos ie 2 right Sopranino units on top of my right TAD 2404 speaker & 2 left on top of the left TAD, and they make a considerable difference easily noticeable. Quite a number of instruments produce harmonics way above 20 KHz and we perceive them. There are studies showing this eg see James Boyke, "There's Life Above 20 Kilohertz! A Survey of Musical Instruments Spectra to 102.4 KHz" and how we perceive sound. If you don't accept this, fine. We are all entitled to our own judgements. I will stick to the ones based on what I can clearly perceive. I am now wanting to add a super-tweeter on top of each Rey Audio KM1V speaker in my secondary system.