difficulty in mounting rail to new LB

My gunsmith is reluctant to drill my newish Les Baer for a rail mount as he says he hates to mess up
a "fine pistol".  It has sights on it, which would require drilling in the spot where the rear sight is now.
Is there a solution to this that does not require a new slide?

Are you removing the rear sight? It’s common practice to drill another hole where the rear sight WAS before being removed. I’ve also added a new hole to the rail when necessary to get another screw location. Sounds like your gunsmith hasn’t done many rail installations. I’d think twice before using him. I see lots of botched rail jobs:(
Jon

Jon Eulette made and installed a rail on my Les Baer P-II that does not interfere with the existing sights, and works very well.  He did not need the whole gun, only the slide.  It is very quick and easy to remove the rail and use the iron sights.

The turnaround was very quick.  I recommend Jon's work.

If your gunsmith doesn’t feel comfortable doing it, you should pass.

Maybe try javaduke and let him make you a dovetail picatinny scope base like this

maybe the best option, although I infer from Boxturtle's post that Jon has a rail
that leaves the sights alone.  Hopefully that would be easier and lower mounted.

+1 for Jon’s rail and his services! He cut his rail to fit my SARO without removing the factory Target sights, turn around for slide only was very quick. Jon has been very helpful to and very giving of his time and expertise both with me and to the list. Jon is working on a build for me now and like many others on this forum I’ll be thrilled to have a Eulette built Bullseye gun!