Just in case someone wants to take an alternative approach.
See attached an original production design concept of the Cross.
Picture courtesy to auction at Bonhams:
Bonhams auction
Don’t think he will do that. Seems like it took him ages to finish it.
Besides, this is handmade stuff and the basis is Magnolis diary. To make a run you would need to go either „Holt style“ = hand write each diary or disassemble each diary to be able to print the single pages.
A lot of work...
Since the movie plays in the 30s the pocket watch suppose to match the style era of that time.
I‘d say check for chains with a t bar and clasp that resemble the Victorian style.
Below you see my chain I found on eBay.
Nice work.
A few things though you may want to consider:
The original seems to be slightly thinner.
The carvings seem to be slightly deeper and carving lines may be slightly thicker.
But that’s my „gut feeling“ when looking at the movie pictures.