Hi Rick, thanks for your question. It is not possible to manually add the ends to the wire, which is why we sell cables with a plug on one end and open wire on the other. We have these for both our standard-size plugs and our Pico plugs:
With either of these, you could use two (one on either end) and any length of the twisted wire in between. You'd just need to splice the wires together and you'd have your cable.
If you'd like us to make the custom cable for you, we can do that as well for a small extra charge. Just let us know. Thank you!