Sorry, I wasn't clear enough in my original post, but I appreciate the response.

The latch is missing. It looks like it is just a bolt on part. The hinge itself appears to be in working condition. I don't want to have the frame welded, I think it is somewhat collectible and I'd hate to do something permanent like that.

If I can't find a proper replacement, I think I can probably cobble something together with some long bolts and metal plates etc.. If someone has already done this, let me know.