According to this
your TV has composite and headphone audio out jacks. You just need to get a set of wireless headphones, and you're good to go.
I bought these Sennheisers to use in exactly the scenario you're describing, and they work very well.
I think they were cheaper at the time though... more on the order of $70 than $100.
EDIT: Oops! Sorry, when I was copy/pasting the model name I left out the 5 on the end. It looks like the P42G25 does not have analog audio out, which makes your objective much more difficult. Unless you can find a set of headphones with TOSLINK input (which seem to be quite pricey), I'm afraid you're out of luck. Maybe the cheapest option would be to try and find a DAC that supports optical, but that would probably be just as expensive as a cheap receiver.