Screw-in Birthstones

A customer of mine has brought in a mother’s ring with a missing
set. It is an old style-the birthstones are imitation, 3mm and the
crowns are in white gold. The crowns screw in from inside the ring. I
need a November. Does anyone know where I can get one?

Thanks in advance.
Dale Pavatte
Diamonds For You
Decherd, TN