At one time there was some 9mm specific slides but the only difference between them and the 38 super slide was the width of the breech face.
I think most of the slides will accommodate both cartridges now.
I have a commander size gun to build and it's either going to be 9mm or 38 super, maybe both.
I built a client a commander in 38 super comp, after test firing the gun I enjoyed shooting it so much I hated to call the gentleman and tell him his gun was ready.
Best Regards
Bob Hunter
www.huntercustoms.com