Julie, it is still not clear what you are asking for. Making assumption...
For PCOMM: in your ISPF application, you would still define ZPF19 as you desire.
From the PCOMM keyboard utility, you can re-map the keys. First, select the 'n' key. Then assign 'program function key 19' to the Ctrl key.
For my use, I mapped Ctrl-F to PF5. So when I press Ctrl-F, it issues PF5 and works as a RFIND (repeat find).