I just simply love fabric-braided cable.  Any fixture looks a touch higher-class using a braided cable instead of cheap PVC cords.  Here are some suppliers that I’ve found:

FabricCable is a UK manufacturer that in addition to a full range of cord also offers a pre-made festoon system.

Sundial Wire is a US manufacturer with an extensive range of cord:

Techflex doesn’t make braided wire, but they do make braided sleeves that can wrap a variety of other wires.