safe emailpetition.php from next updates

Hi,
is there an option, to safe the file “emailpetition.php” in a place, that won′t be overwritten in the next update?

I just need “Mr” and “Mrs” in the droplown-list and not Dr.,Mx. and all the others….

It is great, that I can safe the files petition.css and petition-widget.css in the theme folder, to protect them from the updates but it would be perfect, if I could also safe the .php files.
Any option for that?

thanks a lot
nice greetings
Sandra