Hey Ed!, long time!
There’s obv several ways to produce them, but the cracking makes me think one of the methods mentioned above might have been employed. It’s possible the originals were hand–carved and the pictures show replacements applied later, but without the provenance of the house there’s no way to be sure.
To produce them today, the easiest thing probably is, as mentioned above, to just buy them.
Next easiest depends if you have a CNC or not. You could then either have it make the mold for mass production via the methods mentioned above or have the CNC make them directly out of your preferred material.
If no CNC, you could buy some casting resin and other mold-making supplies and make your own mold. This would be inexpensive, but given the cracks, would take some touch-up work after the fact, and if you’ve never done that kind of work, might take a few tries to get an acceptable result. This obv depends on being able to remove one of the pieces intact, which is not a sure thing.
Most challenging, but imo the most rewarding would be to learn to carve them yourself. Again, the pictures you showed suggest to me that it’s an applique, so perhaps that will make carving them slightly less challenging.