You can see one working on Mukeboy's site in his post click here
You don't actually need to put in a text size changer for accessibility -- you just have to make sure that your sizing is fluid so that the end user can change the text size for him/herself. To do this you can't have your base font size in pixels, some browsers won't resize it, so use one of the keywords instead: probably medium or small. Keep all your other font sizes relative (using x-small, large, x-large, etc. or percentages) and the result is that when the user changes the text size via their browser the whole page scales with it.