I did something like this over 30 years ago. I had to use aligator clips and open the cabinet and find the location of the speaker. Clip the two leads one each to one of the terminals of the speaker. This may work but be VERY CAREFUL NOT TO TOUCH ANYTHING ELSE. I know you'll unplug it. Even unplugged, some of today's TV can store a lot of power and you can also ruin the whole thing by shorting across two charged circuits. From the description you won't have stereo in the TV so you might want to just try one speaker. See if the TV speaker indicates its Ohm rating for resistance. I think adding a second speaker of the same resistance may actually half the resistance rating, but I'll leave that to one of the engineers to explain. Heck I'm not even sure they make these cases so you can open them anymore.