I checked around the usual places and there aren't any listed in stock. Probably best to call S&W and ask for someone in the parts department. Have your serial number ready when you call. They will need the serial number to ID the correct parts.
1-800-331-0852
Parts lists are here....use the forum link:
PDF's of the Parts Lists
It appears from the parts list that the correct center pin is part# 21499, and the ejector rod number is 21501. Some minor fitting may be required.
Carter