Smith and Wesson Model 41 rear sight blade is all the way left - need to center entire rear sight assembly

My model 41 rear sight blade is all the way to the left and I have no more windage adjustment if I need to move the POI left. How do I fix this? Right now the gun is zeroed at 25 yards. Thanks in advance for any help with this matter.

If memory serves there are two different rear sights on an M41 depending on the vintage.
One will have a little set screw on the top tight(as looking from the rear while firing as normal), that will have to be loosened or just remove it while you adjust it.
The other does not have the set screw to lock it in place.
Either one will have to be drifted in the proper direction.
Since yours is all the way to the left then you need to drift it to the left.

This is what I would recommend doing but others may have a different approach.
Adjust your rear sight blade back to the neutral position.
Fire a 10 shot group.
Measure the center of the group to the center of the target.
50 ft would be good and is what is used for my example.

At 50 feet to the target and with a 6 inch'ish sight radius works to about .007" of sight adjustment per inch.
So if you are 4" to the right, then you need to drift the rear sight to the left about .028"

Not going to tell you how to drift your sight cause I do not know what you have for tools and equipment and your skill level.
Do not want to see you damage your pistol in any way.

Best I can do over the internet.

Thank you C. Perkins. I have a decent skill set, not close to a gun smith but I have replaced rear sights on other guns, etc. I am afraid to try and drift the sight over as I looked at this method today and don't see a way to "unlock" the sight from the barrel. FYI, I have sent this to Smith and Wesson for another issue, twice, and asked them to do this for me. They did not either time. They have the worse customer service ever. I will probably not buy another Smith and Wesson product unless they correct this issue.

I'd count the click from one extreme (full Left to full Right), obtain some type of small level to set up a sand bag rest with the pistol sights level.  Set up a black dot paster about 15 yards away. Center sight windage by halving the full range of motion. Loosen rear sight, insert laser bore sighter into pistol, push sight in direction until it centers on target. You don't need ammo to do this. I typically this indoors in my hall way at home to obtain your basic zero.  Should be on paper when you go to range and need no more than a few clicks to be in the center. Massive adjustments may indicate you are canting your pistol or maybe eye dominance issues. 

Good luck!

what length barrel and what year is the pistol..

some of the later rear sights are Keng sights that look like Bomars..