William: The lever you refer to is on the left front of the frame and acts both as a slide block and a barrel lock, if this is the lever you are referring to, and if so, replacements are avaialbe from either Gun Parts Corp., SAMCO or SARCO (I think).
Re: 'the pin'
There is a detent pin that locks the lever into the frame that cams on the surface of that lever during takedown but I have never seen one broken and cannot imagine how one would break it unless someone attempted to force the lever out. If the gunsmith said the lever itself was broken then it can be replaced. If the pin that holds the lever into the frame has somehow broken then that should be replaced as well.
One of the last two or three Shotgun News issues carried a extremely informative article on the P-38s and I would refer you and your associate pastor to that article - it may even contain information on contacts and repair services for those pistols. Some of the clearing houses are advertizing P-38s and may list parts availability. HTH.