Z900b brake master cylinder

Hi. Newby here. I purchased a 1975 z900b that has been restored 10 years ago then sat idle. I bought it through a 3rd party so cant get the history on it. The front brakes were locked. Managed to free them up & put news seals through the calipers but the master cylinder is not behaving. The lever works freely but obviously needs a kit as it doesn't pump. 
My problem here in Australia is that l cant reference a master cylinder that looks like mine to get parts.
It runs twin discs mounted behind the forks. The brake hoses run direct from the MC to each caliper. The MC has an inbuilt brake light switch. Also, l cant remove the hand lever from the housing to start at the the repair.
I'd like to purchase the complete MC but cant find it. Any other type requires a pressure switch & mounting & different lines.
My MC has the round plastic reservoir.
So after all that rambling, could anyone identify what system l have & how best to get me going (stopping)
Cheers, Mick 

Welcome to our fun!
Doesn't sound like your front brake system is original Z1, nothing wrong with that but some pictures will help identify what you've got.

Welcome from the UK

Sometimes the master won't pump because it needs to be primed first.  And if the old brake fluid was full of sludge, the small return port may be plugged up also.  I'd take it apart, inspect, and clean.  Again, make sure the tiny return port is open.  You may need a piece of wire to poke the hole.  

As has been said, pictures would help, but based on your description, this is what you’re looking for:  4into1.com/kawasaki-master-cylinder-w-clutch-lever-set-15-8mm/

Make sure you get the right bore diameter though. You should be able to find a number, usually a fraction like “1/2” molded into the body of your mc. Whatever you get to replace it needs to be the same diameter. 

The normal configuration for the Z1B with dual calipers is a single hose from the MC down to a splitter mounted on the lower triple tree.  Two hoses exit the splitter...one for each caliper.  The MC is larger (taller) than the original one because of the increased volume required for two calipers.  From memory I think the piston fits a 5/8 inch bore compared to 1/2 inch for the original MC.  The OEM brakes on a Z1B are made by Tokiko.