Think about using an orifice plate, although they can significantly change the system hydraulics if sized badly.
ie, the raw hydraulic power from the source shall have to overcome a greater hydraulice resistance within the pipe system.
Also orifice plates are generaly considered to be an economic option, ie cheap.
Also,
Control butterfly valves can be used on certain applications in place of a globve valve assist with restrict flow.
Review CV value losses for diferent types of valve ?