Good day,
I believe you actually need a RJ12 cable (RJ12 connectors on 6-conductor cable). RJ12 is the same connector as RJ11 except that it has 6 loaded pins instead of the RJ11's 4 pins. Also, I believe that the RJ12 cable is used for Zonebus and not N2... well, at least I have never seen JCI use their RJ12 cable for N2 communications.
As for the cable itself... it does not need to be from JCI. It is typical telephone cable that has 6 conductors. You simply need to ensure that the cable end wiring matches up... RJ12-Pin1 on one end goes to the RJ12-pin1 on the other end.
Cheers,
Sam