The OEM ones were something like $8 for a 3-pack many years back. Seemed high but they last a while.

There are tons of them on ebay. There are a few different types, depending on your thinkpad model. I suspect the T480 uses the square post style like older T series thinkpads, but I don’t know. Basically, look carefully at the pics to make sure you get the right kind.

If you want OEM ones, try lenovo.com, but they will cost more.

If it is only down 30-40% then just keep using it. Mine is down more than that and I can afford a new one but figure I am ok without it.

I don’t understand the purpose of this new license, and inventing new licenses has always seemed like a terrible antipattern to me. I’m content with GPL3 or Affero GPL3.