find / -iregex not working as expected

[Michael Convey]

I'm trying to find the following files with a single 'find' statement:

/var/lib/postgresql/9.4/main/postgresql.auto.conf
/usr/lib/tmpfiles.d/postgresql.conf
/etc/postgresql/9.4/main/postgresql.conf

I tried the following (and more), but I can't figure it out:

find / -iregex "*postgresql.*.conf"
find / -iregex "*/postgresql*.conf"
find / -iregex *postgresql*.conf
find / -iregex '*postgresql.*.conf'

What am I doing wrong and why?