Filter, changing filter media or buy a new filter?

[corrado95]

I live in Thailand and bought the house in 2016
The house with pool was built in 2010
The owner installed a Magnapool system.
When I bought the house I realized that the chlorinator was faulty. I saw the special salt was expensive and I read that these system was a scam.
I then installed a regular chlorinator and started to use regular salt.
Now I can see that it's time to change the media in the tank.
When i look in the manual it says that it should have Diamond cleen M10 120 kg and M20 40 kg.
I don't know if I can buy that in Thailand. Is that some kind of glass beads?
I guess this filter comes from another company, is this also a Poolrite product as the chlorinator was?
Can I use another product for the filter media? Do it have to be two sizes?
I am very grateful for the help I can get for you people in Australia!