Thanks and a correction
Thanks for steering me to Earl's Repair Service. I'll add them to my contacts for future reference. Before I asked my question about sources for the mag extension, S&W sent me an email stating that they didn't offer them. After I posted my question on this forum, I received an email from a different S&W rep who told me how to get the extensions from S&W. I have two on order, but like a lot of other weapon parts, they are back ordered.