Try using Ruby Script. There one for AWS:
You should find one on Github. Make sure there is Ruby installed first. Also, I don't see a reason why it shouldn’t work on an existing cluster. EMR runs bootstrap scripts after all the selected EMR components are installed, Hadoop user created, and config settings applied. Of course, you'd test this on a new cluster, so you don't break your persistent one.
Make sure you use SCP or S3 because your script would run on every node. Also make sure you pick up the latest version to stay updated and installation to happen smoothly: https://drill.apache.org/download/
EMR clusters are bound to tear down. To ease this process, we have bootstrap scripts & cluster configuration. You may want to boot up, run job, tear down. This would be more affordable.