Hello Rob and thank you for your post.
What you saw on other posts is correct; the internal wireless adapters cannot be exchanged/upgraded by anyone but the laptop manufacturer. The reason for this is because the laptop manufacturers have to customize their systems to prevent “unauthorized” hardware changes. Any change to the wireless (or other internal devices operating on radio frequencies) may cause their system to no longer comply with strict FCC and IEEE regulations.
Now to what you can do, if Lenovo has a version of your system with Intel adapters then you may ask for any Intel® Centrino® wireless adapter, but if they do not have any other wireless adapters for your system then you might need to look for other options of streaming content to your TV, just search on the web for “streaming content to TV wirelessly” and you would be able to find other options that might work better for you.
I hope this helps.