If you are looking on how to install Coastal Tech's Cruise Control switch, you will have to buy it. But if you want a EV button you can you your self, I did, I put it on my Brights Flasher, but most make a button from Radio Shack. It took me about 30 min to do. Just look at the EV Button Insallation Instructions done by Evan Fusco and others. Be sure to read all disclaimers.
It works very well. At first I didn't want it when I first installed it, but now I am using it alot. In parking lots, to move the car to wash it, anytime you think it would be useful and no use for the gas engine.
There has been much talk about the problems it has. Some of the few I have heard:
i) Sometimes might not engage EV.
ii) Sometimes might not disengage EV.
iii) Cancel button might not work at times.
These are just some of the things that I have heard, but they happen seldomly.
Another thing, even the EVb most people install, like the site I posted above, has some flaws. I know mine does. It has i) and ii) sometimes with my Flasher EVb.