SW M41 Rear Sight Issue

Recently picked up a SW M41 5.5” barrel  here in Commercial row. The barrel has a Millett rear sight, best as I can tell and for some reason I can’t get the windage adjustment to work. The windage screw turns as normal, but blade won’t move. Not sure if the threads on the screw are messed up.
Doing research, looks like Millett used a proprietary dovetail that other rear sights will not fit. Do any of the experts here know which model of the Millett sight was used on these barrels? Series 100? I saw some Millett sights on eBay but hesitant unless I know for sure that it’ll fit the barrel.
Any other suggestions or solutions? Appreciate any and all feedback. I can post pics  of the sight if needed.

You should be able to change out the rear blade from the same series sight without removing the body.  Be aware that there are some funky springs that are easily lost or damaged and that there are several blade heights.