Here you go...
http://www.fastenal.com/web/search/products/fasteners/sockets/flat-socket-cap-screws/_/N-gj4wbuZjuetemZjudql8&Nty=0
You have to do some work though,
click on length,
click on drive size.
write down part number,
search for a store near you,
http://www.fastenal.com/web/locations
phone to order, as it may not be in stock at that store