A silicone mold is the only way to go. Use Dow "J" or "M" base / catalyst to get a resilient mold. You may need to do two molds, one a positive the other negative. Should be able to produce approx. 40 metal pieces from a good mold before quality begins to suffer, the detail is amazing.
The original part must be cleaned to remove all wax, there is an aerosol "Safe Solvent" designed to remove silicone but will work in this application. This is also a Dow Product but under a new nomenclature since they bought out Dow Corning.
After cleaning it is sprayed with several light coats of silicone release spray and allowed to dry before positioning the piece in a slightly larger box. The well mixed 2-part rubber is then poured in. Sometimes it helps to leave the mold in a vacuum chamber or vacuum-bag it while curing to remove bubbles.
There is plenty of how-to videos out there on mold making, my advice would be pay for the superior materials. We are talking 2- 1-pound Kits.

Here's an idea for replication: Reach into your wallet. Remove $75. Send it to Pinball Life. Duplicate made!

https://www.pinballlife.com/nip-it-alligator-plastic.html

Don C.