If it's small signal then a gm-C filter is popular. But gm tends
to vary a lot with applied voltages so you may need to control
amplitude etc.
At such low frequencies you can pretty much neglect shunt
C and series L, I think. The shunt resistance, you'd be hard
pressed to measure with available DMMs and might need to
use picoammeter (if that's not low enough then you are in
trouble).
Using schemes like the PCB guys use (driven guard traces, etc.)
might be used. But I think this is not so necessary when the
IC traces are all encapsulated in silica.