Have you looked at the 4046 CMOS device, which was available from many different manufacturers?
It has a built-in VCO, but you can also use the PLL with external signals.
PLLs with low frequency sinusoidal inputs will have crappy
phase noise. You would be well off to square it up (in a
clean close-in to source location) and then lock to the
squarest edge you can, if you care about purity.
Such low frequecies are probably "off-application" for
many modern PLLs but that does not mean they are
unusable, just that nobody cares about that use.