The GI issue sights on M1/M14/M1A are identical....there are none better available anywhere in the world for use on an "as issued" combat rifle IMHO.
OTOH you may be interested in match sights for M1/M14/M1A.
The NM/2A rear sights + NM front sight run approx. $100 from several sources including Amherst, Fulton, Gun Parts Corp, Springfield Inc., etc. Price may vary slightly from vendor to vendor but stays close to that figure.
A note for those who are wondering about NM/2A rear and NM front sights:
The NM front sight is much narrower than the standard issue front sight. The NM/2A rear sight is capable of 1/2-MOA....that is, one half minute of angle accuracy. One "click" of elevation or windage will move the strike of the bullet on the target 1/2 inch for each 100 yards distance from the rifle to the target. One "click" would move the strike point 1 inch at 200 yards, 1.5 inch at 300 yards, 3 inches at 600 yards, etc. This level of performance in sometimes known as sub-MOA.....and it goes without saying that in order to achieve it you also need a rifle that's built to National Match specs. It is a given that NM/2A sights would *probably* help you shoot any M1 Garand, M-14 or M1A with somewhat more accuracy than with the standard issue sights...at the very least you'd be able to make finer sighting adjustments. IMO you need a NM weapon, or one rebuilt to NM specs, to unlock the full potential of the sights.
As a comparison point the M1 Garand, the M-14 and M1A standard sights are capable of giving 1-MOA....one minute of degree accuracy. A "click" of the sights will move the strike of the bullet 1 inch for each 100 yards distance from the rifle to the target. The M1's "as issued" 1-MOA rear peep sight gives excellent, accurate service for a combat battle rifle. The "as issued" sights are well matched to your standard GI M1 Garand, standard GI M14 and standard civilian Springfield M1A models.