Of course there isn't. This goes against every design principle according to the era during which banana jacks were invented.
When they wanted the functionality you're talking about, they invented the 1/4" telephone jack.
There are dual banana plugs, rarely quad banana plugs. Space wasn't at a premium back then. Components were huge, and consequently panels could accommodate many holes for single-conductor connectors.
Why can't you just use a stereo telephone jack? If you need more current or better RF performance then you have DIN connectors.
I fail to see any requirement that a stereo banana plug could satisfy that can't be satisfied better by common options.
The photo you linked is called a gender changer. It is used to make a female banana jack into a banana plug. It's not supposed to be easy to separate. It can be used as a coupler, yes. But this is only in the case that one of your banana jacks require a gender change into a plug. In which case one of your jacks is going to separate quite easily when you pull, leaving the other with it's gender still changed. And you'll have a harder time separating the gender changer from this end.
Also remember that the banana jack is still one of the most well-respected connectors with respect to surface area contact and oxygen-free connection. It is literally made to minimize skin effect resistance.
This feature is entirely dependent on the spring-loaded plug sides. The tip would offer completely asymmetric qualities with respect to the connection on the side. This is again in contrast to the 1/4" telephone jack, which offers symmetric connection design.
A typical coupler is male - female ( >-— )