Bought a new shower hand piece and it seriously lacks flow.   I could use some advice on options to modify or replace with a higher flow unit.

My old showerhead developed a crack and started spraying water everywhere.

I did some flow testing and estimated that the handpiece was outputting 12L/min and the hose without the handpiece was outputting close to 15 L/min.  I've been advised by a plumber, that our hot water is mains pressure. (house is circa 2010).

Armed with this info off I went to bunnings, looking for a 12L/min shower handpiece.  The best I could fin 9 l/min, so I bought this because the massage function looked nice.  The massage function is nice, but the regular function is awful.  It isn't outputting nearly enough water for my liking in winter.  Certainly, seems much less than the old handpiece.  

Can anyone recommend a handpiece with higher flow - something like 12L/min.

Or, it appears to have some sort of flow restrictor just where the hand pieces screws onto the hose.  What happens if I pry that out? I could replace it for summer, but right now, it's too cold for a bad shower.