South Side Obsolete: Fred Wilner, NOS and original part
I got the NOS door latches from Fred for my '39 p/u. He's barnfind08 here on the barn.
Another good source would be:
James Saccoccio
Gotham Auto Parts,LLC
340 Cherry Street
Bedford Hills, NY 10507 sales@gothamautoparts.com
Tel: (718) 878-3699
Fax: (212) 519-7909
Repops for 40/41 p/u door hardware are available from many vendors as well. I'd check with Joe's Antique Auto first for repops if that is the way you plan on going.