Have you looked at the cables section HobbyKing? Perhaps here find the material you are looking to manufacture or materials.

Cables

So a breakout cable I assume.

Personally speaking I tend to make them myself by soldering another plug to it, that's what I have done with my LiPo balance port connector so I can attach it to both the EZ-B ADC ports for monitoring voltages and to the balance port charger that sits inside the robot.

I presume the same can be done for other cables.

You could use wire splices/scotchloks too however I've only ever used Automotive ones which are rather large. A plastic cover which houses a metal blade with 2 grooves in it, one fits over the existing cable and the other you can attach another cable to, the blade is conductive so the new cable is joined to the existing...

But these may be too big for what you want, not sure if they make smaller ones than I'm used to.

Thanks for your suggestions, R2D2 and Rich. Pitch is 0.1 inches. I have figured out I can do it with a stackable arduino female header (cheap!) plus a small n-pin to n-pin breakout board, where n is, say, 10. But I haven't been able to find such a breakout board. All the boards I looked at are slightly too big for the space inside the robosapien, and are designed to adapt from one pin configuration to another. I just want to split a 10 pin connection into two 10-pin connections.

I found the magic word!

IDSD-10-D-04.25-S02

Which is just like this:

http://www.arrowcdn.com/part/img/l/2/32/89bfc7b38f01872e54719423a360a1d3.jpg

Except it's all twice as wide i.e. 10 pins wide. Note, there are male pins on the bottom of each connector.

Expensive though.