I have a 5904 with a fixed rear sight. Is it possible to adjust this sight or where can I get an adjustable one?

Thanks.

Buy a hammer and a brass rod or bar and file it to the width of the sight base. Sight corrections are made by drifting the rear sight in the direction you want to move the point of impact.
Remove the slide and position on a piece of wood making sure any
Not recommended for night sights. Use a sight pusher.
Check your firing technique first to make sure you're not manipulating the gun off target. Maybe someone can link to the "pie chart" that indicates what you may be doing when pulling the trigger.

The side to side seems to be pretty good. However, I need to raise the rear sight. I was thinking of shimming it and was wondering what others had done.