Suggest using a small diameter 50-ohm Teflon insulated coax such as RG-178. I haven't looked at my NCX-1000 in a while after spending eons working through its many issues, but believe that coax link you are referring to has small RCA plugs (short center pin) on either end. If you have trouble finding those, drop me a note via QRZ and I'll send you a few.
73 Nick K5EF