@sfishman
Currently FTPS is not supported.
There is an existing open jira to add SSL capability to the get and put FTP processors here:
https://issues.apache.org/jira/browse/NIFI-2278
As an alternative, you may consider using the putFile processor to write your file to disk and then use the ExecuteStreamCommand processor to execute some FTPS supported client from command line to send that file to your FTPS server. This way you can still accomplish what you want to do through an automated NiFi dataflow.
Hope this helps,
Matt