First thing to check is the stop lamp switch located on the upper back of your brake pedal and it looks like it might be a dealer only item, Also I see a taillight relay available from Napa, Give your local Napa store a call and see if they stock these items
There's a new DVD with many chapters on changing light on 1999-2006 Lexus RX 300/330 and the Toyota Highlander. I bought this guys video and it saved me a lot of money. Here's a link http://www.youtube.com/watch?v=Fmo-WcinNhU. I think I paid $50 for the video, but it saved me thousands on repairs. At the end of the trailer, he gives you his email address.