Yeh, the SheaSilverman one worked like a month ago, but I'm guessing Bethesda's having the packs taken down to protect their intellectual property rights.
I was able to make the aforementioned process work by copying the pak files from my Quake 3 installation on my primary PC. If you don't have a retail copy of Quake 3, it frequently goes on sale on GoG.com. Probably Steam too, but Steam hides its files in weird places so I'd just as soon not mess with it. If you're too cheap to buy Quake 3, I mean at this point I would be surprised if you didn't know someone who had it that you could copy the files off of, but the game will still want a retail key to let you play it.