There is 5/8" tubing, and fittings to match, but 1/2" tubing would have a 5/8" OD, and I have seen them as service lines. And of course, the flow is miserable, no matter how high the pressure, so a sprinkler system would have to be laid out in small sections.
If all the interest in water meters comes from a recent purchase of a lawn sprinkler system, then rework the sprinkler system.
If all the interest in water meters comes from a recent purchase of a lawn sprinkler system, then rework the sprinkler system.