You can also import it from the DVD image of SEP12.
Login to the SEPM, go to Admin, Install Packages, Client Install Packages
Click "Add a client install package"
Give the new client package a name, e.g. "SEP11 for Legacy OS"
Click browse, browse to the SEP DVD\SEPM\AdditionalPackages folder and click the .info file there, click Select, then OK and wait for the package to import.
You can then export packages from SEPM in the same way you always have.