That's not really any news, but the nozzle mesh is really just a somewhat but not extremely dense protective metal mesh, without any extra dampening material (can see straight through it to the driver's magnets), aside from what seems to be most likely a wide band of glue, wider than the darker nozzle contact area itself. Although I guess reducing the output diameter like that may by itself serve some acoustic purpose, who knows, but if not, it's probably not a custom part made for PR3 itself.
According to my similarly chinese caliper, the mesh appears to be between 4.4-4.5mm in diameter, so I may experiment with some 4.5mm filter meshes from Ali. With silicone tips the highs are rather harsh after all(but still more bearable than I expected I guess), and I'm not really in favor of wearing foam tips for extended periods of time.