I believe I have those exact same sights on my Springfield 03A3 plains game rifle and 98 Mauser 404 Jeffery dangerous game gun. Does the rear leaf flip down?
View attachment 771071View attachment 771069
Williams Gunsight Co made the iron sights for Winchester. You can order stuff from them directly online. They have hi-viz fibre optic front beads that would probably be the bees knees for you. But with the hood on they don't work much better than brass bead. I painted my 404's front bead with a touch of white primer and that helped. Tried a fibre optic bead a friend gave me and it was an improvement but the bead was too low (Williams sells them in various heights). Fibre optic sights, either front or rear, are relatively fragile but I don't foresee you putting this gun through any hard paces at this stage. The good thing about your setup is Winchester opted for screw attached irons rather than silver soldered. Your rear sight is held on with one screw. Remove the leaf by loosening the windage screw and sliding it off. You'll see the screw for base underneath. Similarly, the front sight ramp is held on by two screws: one half way up the ramp and the other hidden underneath the bead. I would advise buying one of their sight pushing tools to remove and/or adjust the front bead. Instructions for adjusting new beads come in the box. For the rear sight I put another dot of white primer at the bottom of the crotch and covered it with bright red paint. I think florescent green would be better. It helped a lot.
A word of warning. NECG are entirely different sights. They also sell fibre optic bead front sights but theirs slide in from the front while Winchester/Williams are pushed in from side. The advantage to Williams is windage can be adjusted with both rear and front sights. If you go with NECG sights you'll need to replace the front ramp (at least). I strongly recommend Williams. They are great folks to deal with. Take a look at their online catalog. You can drop me a line anytime if you need help.
Keep shooting. I'm also hitting the end of the roundup and know what you're going through. The Grim Reaper won't get me without a fight. And he better go shopping for some brass knuckles cause he's gonna need em. Let's make the bastard work for it.