I have several powerbanks connected to a Y-cable like this one
https://www.startech.com/Cables...
or if that even existed, even a Psi letter(Ψ) shaped "Powerenhancement cable", but unfortunately this cable is nowhere to be found or only at the mentioned shop I don't like, so hop Digitec product manager, please find us something nice at survivable prices XD
{Ach and if you(product manager) should read this right now, it was a damn torture to search for such a cable or other exotics with your filters, there must be more detail, primarily whether you mean socket or plug, as far as I still painfully remember, Microspot has solved it relatively useful, but have in contrast to you again hardly any products in stock, that should not be an advertisement, but only a suggestion for improvement for your immature cable filter system;) I have quite a few orders open right now, you can give me a discount for the golden tip ;D}