Rear sight retaining pin popping out on AMT 1911

Hey guys,

Anyone ever have this issue before? I got an old original AMT hardballer Longslide which I had the slide polished and restored. Not sure if this happened before or not but the retaining pin in the top of the slide for the rear sight backs out a bit after firing some shots or even racking the slide a bit. The hole is not warped in anyway so I’m thinking it’s just an old greased up pin. Anyone have any recommendations for a good replacement pin that shouldn’t back out in use?

I had a similar issue before with the buffer on a 10/22 rifle when I stripped the receiver down to bare metal. But like I said the slide is still sharp and crisp.