I make the carbon fiber back plates. The material is readily available through Amazon. The key is to get the correct thickness. You want to duplicate the thickness of your existing plates, and those can vary on an Alembic depending on whether you have brass, plastic, or wood plates. Then just use your existing plate as a template to trace the shape onto the plastic sheeting which covers the carbon fiber. Then cut out with a scroll saw, fine tune the fit on a belt sander, and drill the countersunk holes, and you are good to go. Wear long sleeves to avoid the severe itching the carbon dust can cause. A mask is also a must.
The weight savings is amazing at virtually a pound. The carbon also is a good RF noise shield, and is conductive for grounding. I have done this on previous basses, and passed on the concept to Alembic, so you may see that as an option soon.
