If you want them quick order from Mouser, Newark, or DigiKey.
If you want wait 2 weeks and are willing to take a bit of a risk of not getting them. (My 4 orders have been OK but others have had problems) order from futurlec.com. They are way less expensive but as I said a bit slow and somewhat risky. I order breakaway and the 2x5's like on the Junebug from them.
Breakaway 2x40
HEADD80 80 Pin .100" St. Male Double Headers $0.50 (.45 for 25+)
For making cables you need
DCC10 10 Contact IDC Socket Connector $0.25