If you must have sprinkers with ½" inlets, you could try Rainbird's 3500 or Hunter's PGJ - these may be taller than your present sprinklers, at seven plus inches. Purely in terms of watering flexibility, their standard ¾" inlet rotors (5000 or PGP) are the best bet, and you can always get a bushing for the larger inlet. Toro still makes the 300 stream rotor head, which is the original that was copied for the home improvement stores, and there are different nozzle assemblies for it, so you might find a match. The 300 has a ¾' inlet and is 6 inches tall. If you are stuck with needing shorter heads, you could try a K-Rain K-1 rotor, which has a ½" inlet.
