According to this ebay auction, it is just basically plug and play. A bit expensive new though.
http://www.ebay.com/itm/2009-2010-Toyot ... 2251wt_952" onclick="window.open(this.href);return false;
I agree about looking for a used one. Try
http://www.car-part.com" onclick="window.open(this.href);return false; looking for for a local 09+ Matrix, Corolla or even Vibe. And after looking at a few other ebay auctions, it looks like the same switch is used in a lot of other Toyota and Lexus models.
http://www.ebay.com/itm/2008-TOYOTA-PRI ... d0&vxp=mtr" onclick="window.open(this.href);return false;
I found that a 2009 Matrix switch is running about $80 or so at
http://parts.olathetoyota.com" onclick="window.open(this.href);return false; but since there are no pics, I can't confirm if it is the add on switch or not. Looks like some Matrix models had cruise control on the steering wheel. Maybe check with a local Toyota dealer parts department and see if they have more info on the switches available.