ECB 3D Printing has created an easy to use universal set of rollbars that you can cut to fit your RC body and glue the bars in to make the body look like it has an internal roll cage. 
 
The front windshield bars are 3.5" (89mm) long. The rear window bar is 6.3" (160mm) wide. The mid bar is 2.16" (55mm) tall. These lengths are made to be trimmed down for the body you plan to glue these to.
 
These 4 parts come in black and the dash board in the pictures is not included.