This has been asked many times before, but they havent listened to the requests.
Offline updating of CIS is being introduced in the next version of Comodo Security Endpoint Manager (CESM). The version of CIS in CESM is specific to CESM installations, however, it shows that they
are listening

and this functionality can and will be introduced to standalone versions of CIS. Exactly when is still undetermined. Now it comes down to patience, rather than ignorance.
You can C&P the signature files from Comodo's folder.
In the interim, you can do as Kyle said and copy and paste the "scanners" folder from an updated system to another, but you will have to temporarily disable D+ (if activated) to do so.
Hope this helps,
Ewen :-)