Just put in a version of 11.x that shows up. The latest version of Cleanwipe will remove both 11.x and 12.1 versions.
Cleanwipe is only available via Symantec support
Obtaining Cleanwipe:
https://www-secure.symantec.com/connect/forums/how...
Methods for uninstalling Symantec Endpoint Protection
http://www.symantec.com/docs/TECH184988