How to copy vius def to isolated network

Hello everyone, Here is my issue:

I have an isolated network that is not allowed to communicate to anything outside itself and has no internet. Within the network we have a SEPM console that all the machines connect. My question is how do I get and copy new virus def to the SEPM console without corrupting anything in the console? Is it possible to copy virus def from an Live Update server and paste it in the SEPM console? If that's not possible what are my choices?

Thanks