Most universals should work with just about any cable box. Since you are probably renting the remote/cable box, let the company know and ask for a replacement.
You can order a cable television remote from numerous places ranging from many retailers such as walmart and best buy to getting them from your cable tv service provider.
The easiest way to get a new remote is to get one from the cable company. The other option is to get a universal remote which is better since it can run several different devices with one remote.