separate irssi services passwords from main configuration file

Question

I want to automatically connect to some IRC networks that don't all support authentication SSL client certificates (like OFTC) or SASL (Freenode). At the same time I want to add my irssi config to version control but do not want any passwords winding up in there. Is there some solution to this problem? How can I add most of the irssi config file to version control without committing the passwords as well? Getting irssi to source some external file for example. Or something that achieves a similar result. Thank you!