this is the breakdown of what I have found out so far from PC

04-05 prius' have the following part numbers:
84720-47010 is for the EV button also known as the switch assy. patern
90980-10964 is for the housing for the EV button.
I have done some investigating and have found a site that sells the OEM parts for under $30. That is the total for both - $25 EV button and $4 housing- This is an unheard of cost so I want to try and check it out first.

06'-07'
I have found it very difficult to find the part numbers for the 06-07 prius' Can someone help? I saw a reference to a 84720-47020, but it seems that Germany and Japan dealers replys are always "not a real part #".---NEED HELP HERE!!!

DIY Install (sorry but some of the links did not work for me so I have not included them)
04'-05'
http://www.scubadivervideo.com/Files/factoryEV.pdf
http://www.calcars.org/prius-evbutton-install.pdf

06'-07'
http://web.mac.com/gagix/iWeb/PriusMods/EVButton.html
http://www.evnut.com/prius_ev_mode.htm