This may be the wrong place for this, but I've been looking for a while and can't find what I need, so here goes:

Situation-I've lost about 60% hearing in my right ear, but only about 15% in my left.  Mostly I listen to audio through a set of Sennheiser wireless headphones and their only input is a 3.5mm stereo plug.

My signal source is an old WD TVLive box.  It's output is fed to an HDMI signal splitter that outputs optical that I feed to a soundbar but has no other audio output.  The HDMI video is fed to my tv.

My tv has 3.5mm out which goes to the headphone transmitter.

What I am looking for is an inexpensive box to go between the tv and the transmitter that I can feed stereo audio in, and then adjust the volume of each channel-louder for right, softer for left to balance what my ears can hear.  It doesn't need to do anything else.

I've found a few things that let me adjust volume, but nothing inexpensive that allows different volume settings for each channel.

Any help at all will be greatly appreciated.

https://en-us.sennheiser.com/tv-headphones-stereo-hd-65-tv

Thanks for the link and they're going in my possibles list but I really need wireless.

I wear the phones while moving about my apartment doing housework and working in three different rooms.  I would need at least 80' of wire.

They have a couple wireless sets that might work, but I'm a retired old man whose ex-wife managed to snag almost half my pension, cost is a major factor.

Features & details[ SPECIFICALLY DESIGNED FOR ] 1) the hearing impaired, seniors, or for those in need of a solution to watch TV at their own volume; 2) those who prefer around the neck style rather than over the ear headphones for easy operation and comfort.
[ MULTIPLE FUNCTIONS ] 1) Left/Right ear balance control 2) Volume control 3) Enhanced High Volume 4) Three preset audio profiles including Bass, Treble and Balanced mode 5) Mono or stereo mode 6) No audio delay
[ WORKS WITH ALL TVs ] HT380 Digital Wireless earphones set is compatible with all TVs on the market. Even if the audio out port is not accessible, you can use the microphone to pick up sound.
[ VERSATILITY ] Works with any of your preferred wired headphones or earbuds. Enjoy all-day playtime with the rechargeable battery plus an included spare battery conveniently stored on the HT380 base.
[ HEARING AID SUPPORT ] The HT380's neck loop was specially designed with telecoil for wireless access to transmit and amplify sound to your hearing aids. Also, be aware of your surroundings or enhance conversation by using the "Ambient" function.

Thanks. I did not see those when I was looking at Amazon.