Coaxial DC power cable for switching AC adapter required?
AC-DC adapters for laptop power supplies are of switching type. Therefore they do have some ripples, and the ripples can cause unwanted RF emissions. To mitigate this, manufacturers prefer to use "shielded" power cables, using coaxial cable construction. It is not a RF cable, but coaxial. I am not sure which particular cable they use, but as a good approximation you can look for "single-conductor cables" with "shielded" property, for example the Tensility cable (found via Digi-Key engine).