You got a real Winchester or the Japanese copy?
If the copy does it HAVE a tang to put one on?
Do you want a "sporting tang sight" like a Marble's?
They are still there.
Check at Brownells and Midway.
Or do you want a vernier tang sight for serious target shooting?
The guys on the Shiloh Sharps board say that Ron Heilman's is the least expensive one worth having.
Ron Heilman Sights: Ron is a craftsman of the first order. Ron makes Soule sights in short, medium and long range configurations. The sights can be had with vernier markings on either side, depending on your choice. windage adjustments up to 40 minutes are also available. Ron also makes a spirit level front sight. The level is inside the globe, and the sight uses Lyman 17 A inserts. Prices for the tang sight are from $225.00 to $275.00 and the front spirit level is $110.00 Ron can be reached at 253-840-2623 or firstname.lastname@example.org
Me? I use Baldwins but they are out of your price range.