Like @Open1Mind I tried various options and about 8 years ago went to custom moulded in ear speakers wired externally to the Sena S20. Does not address your concern about having wires run out of the helmet to the exterior, routing those wires when you take your helmet off etc, etc.
I used a guy that goes to the international bike show that trips around the US, they mould your ears at the show and then produce them and mail them to you. Expensive, but they have lasted 8 years. They are of the quality (I am told) that musicians use on stage.
I do not have the brand in front of me, but there a few companies doing this.
Vince