There is an option to install SEP client with the latest update.
http://www.symantec.com/business/support/index?page=content&id=TECH104779
Or as said above you can install the latest definitions offline by downloading the IU and executing it on the client manually afer an install. the definitions are available in the below link.
ftp://ftp.symantec.com/AVDEFS/symantec_antivirus_corp/