Reddit reviews How to Cast Small Metal and Rubber Parts (2nd Edition)

For something small and detailed like this where you only want one or a couple I would definitely go the lost wax casting route. That is the sort of casting that is done for jewelry.

This book:
https://www.amazon.com/dp/0830604146 How to Cast Small Metal and Rubber Parts (2nd Edition)

Might be useful.

Now if you want to make a large number of them then you should probably go the create a die and press them route.