Unfortunately, this is not something that we can do. Our Julbo RX LAB sunglasses are made in a specialized optical lab at Julbo France. The prescription lenses are custom made to fit each individual frame. A big part of the process is to properly fit the Rx lenses into the frame.
If you have a Julbo frame that is in decent condition that you want to use for prescription, we recommend asking your local optometrist if they can do that at their lab. We also work with Opticus.com and SportRx.com closely and they might be able to help!