Obviously, if I can't find a single control to run both fans, I'll just
install a 2 or 3 gang box and use standard controls.

Anthony

Anthony, even if you find a single control for both fans, it
would not fit in your "1/2 depth" outlet box. seems you'll have
to make other arrangements. Is there perhaps a 'kinder,
gentler' place to put the new box (wood rather than lath)?

lee h