Hi Lim,
The RJ-21 is a 25pair cable with a Male Amphenol end that connects to the VG. This cable is not ordered through a Cisco supplier but normally through a supplier of Telco products.Is there a company in your area that sells voice "line cords" etc? If so they will probably be able to source an RJ-21 for you that is made to order depending on what length of cable you need.
Hope this helps!
Rob