I know the best option would be to go back to component builder and fix to add an extra item to an enumerator field, but I am hoping someone could advise if I could change this in the code after a component is uploaded to a site?
I have had a look though the files but have been unable to locate where an enumerator gets its filtered data from. Any help appreciated.

You will find that in the helper. It is not the best place for the moment is it there.

enumLists()

Found it and made the change. Thank you