You could try using a WIRE SAW<
If you can find one thin enough. It's effectively teeth on a wire. Alternatively perhaps a coping saw blade. You could even grind it down in thickness to suit by mounting it on a timber block and perhaps using a belt sander and some skill.
Wire saw:
https://www.military1st.com.au/pd-pd...4aAmNbEALw_wcB
Coping saw:
https://www.totaltools.com.au/10134-...ping-saw-sj7cp
Best
JA