Five options -
1) if you have an old computer case lying around, you can use the wires that go to the mother board jumpers for HDD LED, RESET, PWR, etc. You can also buy similar connectors from
www.allelectronics.com.
2) I think a CD-Rom audio cable will fit, but you might need to cut it down - Dremel.
3) The motherboard USB headers are the same layout, so you could buy one of those adapters to add two rear USB ports to a motherboard. You can swap wire locations as needed.
4) You could use a HDD or FDD ribbon cable and Dremel off the unneeded connections.
5) You could carefully solder wires directly to the header on the I-PAC.