Fortunately these replicas are kind of soft and easy to work with.
When the front sight on mine broke off, what was left still in the barrel was drilled out slightly over sized, and the sight was replaced with a threaded something or other from my junk box.
Shaped suitable for use as a sight, of course.
The barrel was tapped accordingly and now the front sight is of the threaded type and easily removable if need be.
And it was free and quick.