By saying that your equipment is in a closed environment are you saying that it has absolutely no access to the Internet? If that is the case my suggestion is to contact your Cisco rep or your vendor to discuss your specific situation. Some of our customers also have closed environments and they usually need to get the PLR license with the switch at the time of purchase. Again your Cisco reps would likely be the best POC for assistance.
HTH,
Chuck McFadden