Wall hung bowl with hidden cistern

[glenny]

My parents have 3 toilets in there house all the same but are over 50 years old.
One of them the bowl is cracked and I have been struggling to get a good seal to stop the cistern leaking.
They want to replace the whole thing but I haven’t been able to find a plumber that knows much about these kinds of setups.
The brand is “Sydney Cisterns” which I am guessing was an Australian brand at the time.
Anyway how common are the hidden cisterns? It doesn’t need to be hidden in a wall cavity (ie it can stick out the other side of the wall as it is just a garage) it can be a full sized cistern. Do all of them cost an arm and a leg? Is installation likely to cost a lot more as well?

 

[TomFOhio]

If you are changing the toilet to a different brand then you will probably have to change the carriage
in the wall. I never heard of the brand you are talking about. Yes it will be expensive as it is time
consuming and then you have the price of the wall carriage and new toilet and misc fittings.

 

[glenny]

What is a wall carriage?
After sending photos to someone they have said about $600 to install plus $600 for the toilet. I don’t know if this is a bit excessive

 

[TomFOhio]

The toilet hangs on the carriage in the wall. When you say sistern you are meaning the drain, correct??
Why don't you send us your pictures here so we can see exactly what you have.