We have had this button maker for years now:
http://www.dickblick.com/zz608/06/
I recommend it, once you learn how to use it, you will have buttons made up in no time. This is great to because you can have several people working on the buttons at the same time. One person cutting the paper, one person loading the machine, and one person pressing the buttons together.
You can order the button blanks right from the same website, keep in mind you will also need a good circle cutter and the mylars.
I HIGHLY recommend these ones:
http://www.mrbutton.com/accessor.htm
Do not get one that has adjustable sizes because they are JUNK!
The machine looks expensive, but its worth it.