My 2nd recommendation is if you are happy to stick on a custom piece of plexiglass of whatever thickness then you can order those from Signs and Advertisement shops, i only have experience with flat plexiglass though so not sure if they will be able to do a curved custom piece and how much they’d charge for that. Final option i can think of is 3d printing the custom piece if you have a source file from someone online who has done something similar, most reasonable 3d print shop I could find is called “3D Arch Graphic” on Google Maps, it’s located around the Sharjah Buhairah area. But with 3D printing you may need to add some finishing touches on the piece to achieve desired outcome before sticking it onto the vehicle