Case insensitive exists()?

[Larry Martell]

I have the need to check for a files existence against a string, but I
need to do case-insensitively. I cannot efficiently get the name of
every file in the dir and compare each with my string using lower(),
as I have 100's of strings to check for, each in a different dir, and
each dir can have 100's of files in it. Does anyone know of an
efficient way to do this? There's no switch for os.path that makes
exists() check case-insensitively is there?