How to replace Fowler Dual flushing cistern outlet valve?

[ellenah]

Hi, 

There is a constant trickle from the cistern into the bowl. The flushing outlet valve is the problem and needs replacing. 
Our toilet is an old 9L Fowler (which was bought by Caroma). 

The flap on the side is also broken off (refer to images). 

Ideally I would just like a new flushing outlet valve, rather than replacing the whole toilet/cistern. 

Any advice will be helpful or locating a new part that will be compatible with this toilet. 

cistern valve that needs replacingflap that's brokenflap that's brokencistern valve that needs replacingbrand