A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Tibor Miseta
Date: 2021 Mar 6, 10:30 -0800
Check it here: https://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/planets/
I am not sure, that you really need the de431.bsp for your application (it is HUGE!), the de421.bsp will suffice, if your program accepts it.
(less planetary bodies and shorter time range, but well enough for sextant calibration.)