An original, issue rear sight (marked 'C') is an expensive thing, but they fit the barrel contour of the H&R perfectly.
Re-worked/re-marked 'Rifle sights are available - but I never cared enough to find out where, since I already have original 'Carbine' sights.
The sight base 'will' obscure the top of the lettering found on the barrel, though - that's an issue for some folks.
Scouts Out!