how to use an external dir-locals file?

[Ted Zlatanov]

I have a dir-locals file which I don't want to call .dir-locals.el (it
should not be the default, I just use it for reindenting code in a
particular way).  How can I specify it when loading a file if it's not
even in the same directory?

I looked at the current code but `hack-local-variables' and friends do
not seem to offer a consistent interface to do the above.

Thanks
Ted