Apple doesn't sell discreet parts like this. You could get a new fan assembly which would have a working connector that would be the easiest way but might be costly and difficult to get depending on where you are located.

Sorry to say, I don't know the make & part number of the connector it's self to see if you could find a replacement from other sources. You could try searching the web here's a few manufactures of connectors you could search under: Molex, AMP & Tyco.