Crank Pulley Bolt Size?

[wrongfulleaf]

I recently looked at my crank pulley and noticed that one of the 4 bolt heads has broke. A little odd considering I hadn't touched them in a long while. I was just changing the oil and going to replace the oil pan gasket. I am at work currently and forgot the broken piece at home. Does anybody know what the size of this bolt is or if a parts store would carry it (I'm betting no).

Thanks in advance,
Michael

[georgeb]

It's a 6mmX20mm (est) long. Don't know the pitch but it is the most common one. Take another bolt to make sure. Advance Auto has a better supply behind the counter than they do out front. How do you propose to get the broken piece out of the sprocket?