I have a source for replacement of the windage screw on many of the Thompson Center Seneca, Patriots, and Cherokee guns. The screw is listed on Ebay. Took a fair amount of time and at no small cost to get these made up. The main thing to remember on those sights is there is a small hidden positive lock screw holding the windage screw in place. It is described in the owner's manual but most of those are long gone and people do not remember or know about that lock screw until they have ruined the windage screw. Also many of those set screws have rusted in place after having been setting for many years. First make sure the gun is not loaded. You must depress slightly the sight blade, unscrew the elevation screw, raise the sight arm, set the tension spring to the side, then the positive lock screw is accessible on the right front side of the blade adjustment block. Loosen the set screw then turn the windage screw ccw to remove it. Put the new screw in to adjust the sight blade to where it was before. Snug the positive lock screw, replace the spring, lower the sight arm then reinstall the elevation screw