The knobs are really not car specific. Just thread pattern specific. In essence, you can actually take a design to your local machine shop and have them make you one with the apporiate thread.It might be if you don't care how it looks and if you live in the USA.
It's much harder to source anything unusual over here, and the whole point of being on a model-specific forum is that you can benefit from real experiences other peolple have had.
I keep a small sock under the cupholder assembly in the summertime. When I park the car, I'll pull out the sock and put over the knob. It helps a lot with the heat.I have the same one without the color. I love it. except for the fact that its as hot as a m______ in the summer.