http://www.twincityknitting.com/foot...icial_sock.htm
Here's their contact info:
710 First Street East | PO Box 1179 | Conover, NC 28613 | Telephone: 1-828-464-4830
Disclaimer: Twin City Knitting sells through an establish network of sporting goods dealers.
Some other manufacturers-
http://www.trenwaytextiles.com/
http://www.profeet.com/football.htm