Where can I get a screw retained full contour implant crown without a titanium base?

Does anyone know where I can get a screw retained full contour implant crown made without the titanium base? Why can places mill an implant abutment out of solid zirconia, but not a full contour crown for implants?

Why can companies mill an implant abutment out of solid zirconia, but not a full contour crown for implants?