Hello from a new Diana 25D owner

My granddad found it in his barn, and it functions and is in fair shape. There's some surface rust on it but nothing deep, and the stock could benefit from a nice refinish which I plan to do. I can't find a date code on it. It does not have a scope rail.
My biggest problem is that the front sight is missing. Where might I get one? Secondly, I haven't taken it apart but the receiver appears to be stout enough to drill & tap for a scope rail. Any suggestions on that?
I'm looking forward to getting it fixed up and shooting it, so the front sight is my biggest concern.
Thanks!