Replacement freehub bodies for generic, branded non Shimano hubs are pretty difficult to find. The problem is usually identifying the hub manufacturer and then tracing a part number. Even then replacements are either impossible to find or disproportionately expensive.
It's likely the hub you have is made by Formula, Joy tech or Novotec.
They can be found, but for example I've had to source a Novotec part for a modern 'Planet X' branded hub directly from Taiwan. It was for a customer and it took about six weeks to arrive.
This is one reason why I like Shimano and Hope hubs.