Hi, I had a set some years ago that had an infra red Tx. that plugged into the phono socket. My phono socket did not switch off the speakers when in use. The Infra red Tx. was directional and only worked in line of sight. The headphones had a battery in, all adjustable for volume and all worked well. I think they cost about £90 and were a present. They have since failed and seem un-repairable.
If you want wireless system or wi fi system then this may well be more involved.
My own problems were sorted out 18 months ago with some good (NHS) hearing aids.
I would like to know if you come up with anything, that is if it is not too dear.
regards Roy