Check out http://www.pricewatch.com/
for a wide variety of vendors. Atleast you will find out what a fair price is for the part.
I have found the folks that this site to be very helpful, but they do charge a bit more. They have a toll free number. http://www.motherboardexpress.com/
Some vendors sell units on Ebay. You can check the feedback for those vendors then back track to their website where you can buy diretly. Watch out on ebay as many vendors put units together with less than quality components.