You may want to consider an amplifier. I've got an older version of this one that I use when traveling, it is fantastic:
This one however, is cheaper and is pretty well reviewed on Amazon:
You can actually get an even simpler setup with a component splitter that has female ends piggybacking the male ends. Example. This is different from the one I have used for years so I cannot vouch for this specific model. Unfortunately, they seem difficult to find these days just based on some quick searching. Once you have this splitter, you can plug the console into the splitter and the splitter into the TV. Now the sound is working perfectly for your opponent, and there is a 3.5mm headphone jack for your headset to plug into.
In order to control the volume you will want an amp. The one I have used for many years with no issue and highly recommend is the FiiO amp. It has pretty long battery life, can be easily charged via microUSB, and has simple volume controls. I bring a long male-to-male 3.5mm headphone cord to go from the splitter on the back of the TV to my amp, then a shorter male-to-male headphone cord to go from the other end of the amp to my headphones.
OK, so I bough this amp thing, put the lapel mic in the input, and tried several speakers in the output. Still nothing, not even white noise.