If you have a plastic frame but prefer metal frame style nose pads, you can have metal posts attached that will allow you to add them. We do that here in either standard metal or space-age titanium.
We also retrofit Asian style nose pads to plastic frames that decrease the width of the bridge and lift the frame up so it is in your line of sight. Particularly useful if you have a flatter bridge or if the design of the frame is just a little too wide on the nose.