Custom casting recommendation

Hello, I am looking for a special request piece for a client who’d
like 3-500 of a design in sterling silver or perhaps pewter for a
stick pin. It would ideally have a small section enameled upon it
for a touch of color. They have specified a design, and are a non
profit wanting lower costs. Can anyone recommend a source for
custom fabricating something like this in that quantity on a limited
budget? Feel free to contact me off list or on. Thanks so much!