I use the Sceery ACE 1 Special Elk Call
Have a practice with it. If you are lucky enough to be able to listen to sika calling you can mimic the stag calls. Often a short soft "mewl" can bring an inquisitive stag in, otherwise its the pattern of 3 rising/falling whistles which can make a stag think there is another in the area.
Was out on Saturday morning at first light.....saw three stags "play" fighting about 300m away.....called 3 times and waited.......5 minutes later I was aware I was being watched....turned around slowly to see a stag not 20 yards behind me coming in to see who was whistling on his patch!! There was that awkward moment when I looked at my slung rifle and he decided whether to fight or flight...in the end he flounced off barking away!
The other three ignored me!