Mention to friends, family, professors, etc. that you have this thing in mind and are interested in meeting people that can help/contribute/advise properly.
A co-founder is best "discovered" instead of "located".
I would also question if you need a co-founder yet, and what function do you want them to fulfill?
Focus more on developing your idea (both programatically and conceptually) instead of on starting a company, per se.
Anyone can be a cofounder. Most often its friends, or friends of friends, but sometimes its an interested professor(MIT has a long history of this) or random people in your study group that show an aptitude in the field. I would strongly advise you to approach everyone with your idea, explaining what you hope to achieve and the possible setbacks/technical hurdles to come. Ask everyone you know if they know anyone who does something similar. If they come back at you with a few good ideas, or approach the problem from an angle you haven't thought of, then you have a candidate. Eventually you'll find someone as enthusiastic and interested in the area as you, which is perhaps the most important trait, and its a good indication of the type of person who will stick it out and help you change the world.
http://tom.preston-werner.com/2008/11/03/how-to-meet-your-ne...